I have never used this, as I was learning assembler which for simpler projects is better anyway so that you can understand what the PIC is capable of, but it may be worth a look: http://gcbasic.sourceforge.net/

These might be worth pursuing as well, depending on if you plan to generate code for commercial use or not:-

http://picforge.interfree.it/
http://www.xcprod.com/titan/XCSB/
http://melabs.com/resources/win_ide.htm