I tried Oshonsoft Basic (PIC SImulator IDE, PIC18 Simulator IDE, AVR Simulator IDE) under Linux SuSE 11.1 with WINE 1.1.9 emulator and is working great. That's very good for beginners, and in my case, is a good thing programming AVR's.
Of course, you can register it and use without restrictions. Basic compiler is working and also simulation. Is very possible to be in need to launch the registration at the beginning of every session.
However, there is a problem. Use his own editor only for loading and compiling program sources. For creating/editing, use KWrite but you must configure it to save files in a compatible mode for DOS / Windows operating systems (you know, CR / LF old problem). Want to see on your own? Try to edit or create a new program with the original editor and you will get weird errors, even if your syntax is correct. Hope it helps for someone...