LCDs are one of the coolest things to add to any project right now. You can use them to display things from the speed of your bike, to the amount of room being used up on your RAM. This Instructable will give you a general description on how LCDs work, and how to get started using them. The information provided here will give you enough information to even develop control circuits on any Microcontroller. LCDs are a lot simpler than you think!
Step 1: How They Work
Step 2: Building a Test Rig
printed circuit board with individual contacts
10 4.7k resistors
14 wire ribbon cable
any wire to use for wire jumpers
pushbutton momentary switch
2x8 jumper assembly (an eight switch DIP switch would be better. I recommend that actually)
1 wire for power and 1 for ground to your LCD
LM7805 5v DC regulator (or other 5v regulator)
2 small alligator clips
9V battery clip
Optional if you have an LCD wired to a male parallel port:
female parallel port
Helping hand (optional but very useful)
Step 3: Wire the Jumpers
Step 4: Add the Switches
Step 5: Resistors
Step 6: Contrast and R/W
Step 7: Power
Step 8: The Connector
Step 9: Finished Test Rig
Update 06/13/2008: I added some pictures of a miniature LCD tester that fits in an Altoids tin. This tester has no contrast control. I will simply solder contrast to ground during tests.
Step 10: Using the Test Rig
Attached are some videos of initializing, entering text, and clearing.
You might notice that several characters will pop up instead of one when the switch is pressed, to fix this, you need a Debounce circuit. This prevents this from happening by use of 2 NAND gates in a 74LS00 quad NAND gate and a SPDT switch. Below is the schematic.
As for the parallel port, try LCD Smartie. It is a great open source program with a lot of support and great forums. There is an attached video of me using it. The video opens with windows media player.