Programming an Arduino in C.
I know my new robot runs (and runs nicely) on a ZBasic chp, but I will always have a great fondness for the Arduino, the first microcontroller board I ever used. (I used the PICAXE for a while too.)
Right now I have been programming a Arduino Uno with C. I really like the MikroC AVR C from Mikroelectronika. I am using the free version (limited to like 4k, decent space for C programs!). The full version is kind of pricey.
I then use AVRdude (love that name) to send the resulting hex file to the Arduino non-volitile memory. Works great!