Besides my modular addiction, I'm also quite involved with various digital projects. I'm interested in four basic areas: 1) Microcontrollers, 2) DSP chips, 3) FPGA boards, and 4) Wireless.
NOTE: All vendors want your business! Check out the distributers in your area for free seminars... For example, I attended Texas Instruments' "430 Day" seminar and received a free RF2500 development tool just for attending. Of course, they'll make their money back as I use their products - pretty good investment on their part!
Microcontrollers are available in many sizes and capabilities with prices ranging from a few cents to tens of dollars. Typically a microcontroller is programmed with assembly language or C. Some hobby level devices can be programmed with BASIC as well.
DSP chips are specialized math processing chips. They come in fixed point and floating point versions with 16, 24 and 32 bit capacities. Many audio companies have used the Motorola 56k series of chips over the years, with some notable exceptions using the Analog SHARC for higher end devices. DSP chips are usually programmed in Assembler, C or C++.
FPGA chips can be almost anything you want them to be. That is, you load "cores" into them to make them into microprocessors, dsps, AD/DA units, LCD drivers, or any other form of logic. This flexibility comes at a price - most FPGA chips have no built-in functions, so they won't be able to do anything until you load your core(s). Some form of hardware description language (HDL) is used for developing cores that are loaded into FPGA chips.
Hardware Description Languages are used to define how an FPGA chip functions. Before you get too hung up on which language is best, it's more important to see which tools work with the FPGA chip you are working with...