The two main microcontrollers I program with are the 8-pin ATtiny85's and 13's and the ATMega328. To make things very simple for myself I made a target board with seperate IC holders for both of them (yes I know you can put them into one, but I always mess up which direction to put it in, even though its not that hard). There are lots of target board models to choose from, here is another to add to the lot. One benefit that this one has compared to others I have made is that it has the slots to insert an optional resonator or crystal oscillator. It also has easily accesibly / pluggable 5V and GND posts showing. It works with a 10-pin ISP plug from a programmer. So this isn't the most useful target board, but it fits all of my needs so I'm sharing it :)
Step 1: Materials
small experimenters board
10-pin ISP header
28-pin IC socket
8-pin IC socket
You don't need to include any parts you dont want to use. The only mandatory parts are the 10-pin ISP header and one of the IC sockets (and the board I guess).
Step 2: Schematic
The schematic is pretty simple, but it takes a small amount of thought to place all the wires without making it bulky. You want to ensure the IC sockets are easily accessible.
The schematic is messy I know. The black lines are on the top surface of the board and the red lines are on the bottom of the board (reverse side).
The picture of my soldering job is of the back of the board and is only for reference if you really need it. I can never find any use out of staring at pictures of soldering jobs unless I am 100% lost on the circuit... but its there anyways.
Step 3: Finished
You can now plug any AVR microcontroller into the sockets (that fit right) and use your programmer that way. This is handy when you don't want to build the ISP header into the other circuit you are designing or if you want to burn multiple chips with the same code.