If you've had any experience on the terminal (command line), just use the GNU GCC (3.0?) compiler. If you have a UNIX system, it comes with this. The same for Macintosh (OS X). Otherwise, do a search and download it.
GCC is free, and I would say it's the most widely-used compiler out there right now.
Most UNIX professionals use GCC as part of any IDEs they use, as well as anyone programming on Mac OS X (Project Builder/XCode uses GCC as its compiler).
Note however, that it is not an 'integrated development environment'. It is only a compiler, so you have to learn how to write code in individual files, bring in libraries, and then compile it using either a 'make' file (unix convention), or typing everything in on the command line yourself.
You could also go out and find an integrated development environment. Most of these cost real money. I must say that the Microsoft IDEs are not organized in an intuitive way. I haven't seen any of the others at this point.
Note: You cannot use a third party IDE (or even GCC) to program for the Microchip PIC18. Those IDEs and compilers are configured to compile code for your computer, not the microchip.
They will help you to learn C and figure out how things work, but you will have to use the MPLAB IDE and C18 to write code for the microchip PIC.
I would recommend this book:
The C Programming Language, 2nd Edition, by Brian W. Kernighan and Dennis M. Ritchie.
It defines the ANSI Standard, all its conventions, and the standard UNIX libraries.
You can get a copy via Amazon.com here:
http://www.amazon.com/exec/obidos/tg...lance&n=507846