I intend to add more here in due course
Also take a look at GNUPIC, http://www.gnupic.org for some freeware PIC tools.
I first used this back in 2007 for a project, it was rough and ready back then but has since come on leaps and bounds. The IDE has a good range of features, the compiler/libraries support a wide range (over 1100) of devices and built in hardware. I’m not totally proficient in BASIC but I was able to easily code a few projects using this.
Provide a free version of their C compiler
I have been playing with this, it works well and integrates with MPLAB.
The free version supports the following parts:
but there are some limitations on memory sizes, typically supporting no more than 2K of RAM.
Sourceboost (development stopped?)
They have a BASIC, C and C++ compiler for the Microchip PIC range with an integrated IDE. The device support is good, it covers the 12F, 16F and 18F families.
I have started to use their BoostBASIC compiler for a couple of small projects with some pleasing results. The free compiler supports 2K of program memory, enough for most projects, especially hobbyist ones. There are a number of different licences available, with prices to match the level required. Readily sold in the UK by Maplin and Farnell.
Provide a C compiler for a wide range of PIC microcontrollers.
The C2C compiler has evolved considerably since I last looked at it. It is a commercial product, with an IDE and more. Take a look.
http://www.microchipc.com has many useful links, as the name implies.