This Lazy Old Geek has used a lot of Arduinos. There are a lot or Arduinos, clones, DIYs available.

Which is the best?
The truth is that there is no one best. It depends on many factors including:
A. Your finances
B. Your technical skills
C. Your soldering skills
D. Your application
E. Time and labor available

I am going to relate some of my experiences and very subjective opinions.
I encourage others to express their own experiences. Please send comments.

I actually started using Arduinos because of Instructables. Instructables has several very good ‘Arduinos’. Here’s a few:

DIY-Arduino-or-The-DIY-Duino
It looks like a great Arduino and is very well documented.
It does require making your own PCB.

Standalone-Arduino-ATMega-chip-on-breadboard
Another good one.
It requires use of a breadboard.

Build-Your-Own-Arduino
Another good one.
It requires use of a breadboard.

Ardweeny-2-How-to-customize-an-Ardweeny
If you plan on using an ‘Ardweeny’, I would suggest following this Instructable.

Suggestion: Many Instructables leave pin 1 (Reset) unattached. Apparently this will work but I would suggest pulling it up with a 10K resistor to +5v. An unattached floating input pin can be unpredictable. And can cause intermittent problems.

Caution: Breadboards are very handy for prototyping. I use them a lot. I do caution the user after they’re used for awhile, some of the connections can become unreliable(intermittent). One reason is sticking in connections that are bigger than what the breadboard is designed for. Be careful of power connectors and voltage regulators. Another problem is contaminated components.

Step 1: Freeduino

Definition: Arduino shield compatible means that all of the shields designed for the real Arduino will work on this clone.

I think my first ‘Arduino’ was a Freeduino kit.
http://www.freeduino.org/freeduino_open_designs.html

Features: Arduino shield compatible, socketed Atmega328 (bootloader), USB and voltage regulator
What I liked about Freeduino:
Good quality PCB
Soldered easily
Medium quality parts

One of the primary suppliers is NKC Electronics
http://www.nkcelectronics.com/Arduino_c_9.html
They have a lot of Arduino stuff but I don’t think I’ve used them.

I bought my Freeduino from Seeed Studio
http://www.seeedstudio.com/depot/

What I liked about Seeed Studio:
Great prices (sometimes, look for bargains and sales)
Email support was okay
Lots of sensors I haven’t seen elsewhere

Disliked:
China, so shipping time is long
Documentation is spotty. They have a sensor platform called electronic brick that doesn’t seem to be well documented.

I will use again.

When to use: If shield compatibility is needed. If USB is needed all the time.

Step 2: Anarduino

My next 'Arduino' was an Anarduino kit.
http://www.anatools.com/anarduino/

I used one in my Arduino Remote Control
Arduino-Remote-Control

The Anarduino comes from Anatools.com. The only source, I could find is from ebay.com. They are often auctioned so prices vary.

Features: Socketed Atmega328 (bootloader)
Not shield compatible, no USB, no voltage regulator

What I liked:
Great price (I think I bought two for $20, shipping included)
Great detailed assembly instructions

Disliked:
Cheaper quality PCB, it was very easy to create solder bridges
Hard to unsolder components
Atmega socket was poor quality
No voltage regulator
The only place I could find to buy was on ebay.com

I will use again.

Required: USB-BUB or FTDI cable to program or another Arduino to program the Atmega chip.
Needs a regulated power source.

Caution: The standard USB-BUB connector has an unused pin but it can be jumpered to 3.3V. Do not do that when using the Anarduino as it is connect to ground. I almost smoked a USB-BUB.

I found another solution. On my two Anarduinos. I used an Xacto to cut the ground connection (see picture). it is hard to see but the first two pins are connected to the ground plane. The second pin is connected with three tiny strips of copper. I took my Xacto and cut away those three strips so that the second pin was no longer connected to ground.

When to use: If shield compatibility is not needed. Good for small projects that don’t have a lot of connections. Good for standalone projects that don’t require a USB connection all the time.

Step 3: Really Bare Bones Board (RBBB)

I believe the RBBB kit was created by:
http://shop.moderndevice.com/products/rbbb-kit

I actually purchased three RBBB bare boards from Wulfden:
http://www.wulfden.org/TheShoppe/freeduino/rbbb.shtml
They seem to have better prices when S&H are included
3 PCBs for $8 including shipping.

By the way, I bought 5 Atmega328(bootloader) chips from ebay.com (Anatools.com) for $21.95 with free shipping.

Features: Socketed Atmega328 (bootloader)
Not shield compatible, no USB, voltage regulator

What I liked:
Great price
Great detailed assembly instructions
Good quality PCB
Includes voltage regulator

Disliked:
Nothing so far.

I will use again.

Required: USB-BUB or FTDI cable to program or another Arduino to program the Atmega chip.

When to use: If shield compatibility is not needed. Good for small projects that don’t have a lot of connections. Good for standalone projects that don’t require a USB connection all the time. The PCB has a place for a voltage regulator but it doesn’t have to be used and can be cut off if not needed to save space.

My usage: I did not buy kits but just the PCBs. If you may have noticed, I used a 16MHz crystal and 22pF capacitors instead of the resonator. The main reason is that I’d bought some from Digikey and didn’t have any resonators.

Problem: The crystal is slightly bigger than the resonator and doesn’t quite fit.
Solution: If you install the crystal before the Atmega socket, it will fit. Otherwise I raised the crystal up a little bit so it would clear. Also there is no place for the capacitors so I soldered two together and connected them as shown in the picture. I put a piece of electrical tape underneath where the capacitors went. The two leads connected together are soldered to the ground pin between the XTAL pins. Also this board has pins to go into a breadboard.

In hindsight, I would probably have gone with resonators as they fit better, don’t stick up so much and don’t require capacitors. Theoretically, they’re not as accurate but shouldn’t make any difference for most applications.

Suggestion: When assembling kits with soldered parts, I recommend cleaning off the solder flux with Isopropyl Alcohol and cotton swabs or a flux brush (see picture). While probably not critical for Arduino circuitry, the flux can cause impedance problems. The brown spots on my boards are not flux but probably burn spots from the soldering iron.

Step 4: Arduino Duemilanove 2009

I’ve never used an actual Arduino but ebay has the Duemilanove for about $18 (April 2011). Of course, they come from overseas so will take a long time for shipping.
There is a newer Arduino Uno. The only difference appears to be a different USB to serial chip. I’ve never had any problems with the old FTDI chip.

Features: Arduino shield compatible, socketed Atmega328 (bootloader), USB and voltage regulator.

When to use: If shield compatibility is needed. Good for users who don’t want to solder a kit. These are actually cheaper than most of the shield-compatible clone kits, I’ve seen.

Step 5: Seeeduino

http://www.seeedstudio.com/depot/seeeduino-v221-atmega-328p-p-669.html?cPath=132_133

I actually bought one of these for $22.50+S&H; I’m not exactly sure why I bought it. But it’s a pretty nice board.

Features: Arduino shield compatible, surface mount Atmega328 (bootloader), USB and voltage regulator.

What I liked:
Good quality PCB
Includes voltage regulator

Disliked:
Non-standard power connector.
Cannot (easily) replace the Atmega.
Poor documentation. There are two switches on the PCB that aren’t explained. I think one will automatically switch power from USB to external.

This board has two extra connector pins for Analog I/O that is available on the surface mount version of the chip but not the DIP package. Does anyone know if the Arduino software supports this? I haven’t tried it.

I will use again.

Step 6: BoArduino

From AdaFruit
http://www.adafruit.com/index.php?main_page=index&cPath=19

Features: Socketed Atmega328 (bootloader)
Not shield compatible
One version has voltage regulator and no USB
The other version has voltage regulator and USB
Designed to plug into a breadboard

Similar to RBBB.

While I’ve never used one, I can recommend it because of the quality of products I’ve seen from AdaFruit and the always excellent documentation. I highly recommend AdaFruit products.

Conclusion: Well that's some of my experiences with 'Arduinos'. What about yours?