There are lots of microcontrollers and lots of programming languages. Some microcontrollers can be programmed in several languages, others can only be programmed in one specific launguage. For example, Parallax BASIC Stamps are programmed in PBASIC which is a special version of PBASIC (the nice part is that the software you use to write and download your programs from your PC to the BASIC Stamp is a free software download off of Parallax's website). PICAXE is similar in that it requires a special version of BASIC which you write and download to a PICAXE using free software that you download from the PICAXE website. PIC microcontrollers, ATMEL, AVR etc have a variety of software offerings (mostly written by third parties) that you can buy to use to write programs and compile code to be downloaded to the microcontroller. The most common language seems to be C (and C-like type languages). There are also microcontrollers that can be programmed in JAVA, like the Parallax Javelin Stamp. Some microcontrollers like Parallax's new Propeller Microncontroller has it's own special programming language called SPIN. Confused? Don't worry... it will all make sense soon!