Just out of curiosity, how complex are you looking at making this? What are you useing the LCD for? There's enough software out there already that you can do almost anything you want.
The easiest way to get custom stuff written on the screen would be to use LCDPrint and use batch files or something.
I'm just using Crystal Control at the moment. Though I'm not doing anything really specific right now.
This link has a good example in C, along with some fairly good documentation as to what things do. It's also got some links to other sites. If you want to google some more, I found that "parallel hd44780 control", or something like it, would return the best results.
Anyway, good luck,