I've used the CCS C compiler for PICs for about 5-7 years now. I really like it. Some C compilers don't come with many built-in functions, but CCS does. They cover most all of the PICs except for the 32bit PICs.
You can download their manual for free on their site below:
They also offer educational discounts. However, some time ago, I got a lower-cost license as a hobbiest, agreeing not to use it for any profit venture. Not sure if they still offer that. Their IDE is really good. Their software works with their programmers or Microchip's programmer units.
Another very new tiny development board is the RFDuino. It's just a tiny bit larger than the Digispark, and needs a seperate USB shield for programming. On the plus side, it's got an ARM Cortex M0 CPU, and low energy Bluetooth 4.0 built in. Programming is via the Arduino IDE, with some added hardware libraries and definitions. Many Arduino libraries will work unchanged, as long as they're not too hardware specific.
They're just finishing digging out from under a mountain of Kickstarter backers, so it's still in nthe preorder stage, but at $21 each, it looks very interesting.
Max, I completely relate to your post! I would have killed for these when I was a kid and now that they are out and low cost I just don't have the time to PLAY anymore.. Very sad face. I was wondering what the various programming options are for these boards. Only one really talked about an on line compiler and while I am familiar with the PIC programming they are very difficult (at least the 32bit ones) to configure properly. I would love to see an overview of the free/low cost compiler programming options for these and other low cost boards!!
I can`t believe you left put the king of development boards : Pololu Witcel!! Besides housing the industry standar 8051, it includes a full featured RF link! Avaliables FREE libraries allow to set a UART wireless link in 2'. Priced at 19 dollars this little thing is a bang for the buck!
I'm wokring with the Teensy3 right now and it does infact support the Arduino IDE / language. You'll need to download and install the Teensyduino (URL below) add-on, but once you do you are good to go. You may need to tweak some 3rd party libraries to get them to work, but I am currenlty using the Mirf lib for the NRF24L01 and it seems to be working fine without any changes. So far I think it is a great little dev board with lots of peripeherials and power to spare. I also really love the formfactor, being able to just plug it into a breadboard is great, and for one off's you can just solder it in like it was a standard dip package. It also one-ups the Leonardo in the USB HID area with native MIDI device support, which I think is sorely lacking from the Leonard.