What can be found on a motherboard? Well...
- DRAM chips, usually 1M x 4 bit (ie 2^20 words, each word being 4 bits);
- Static RAM cache chips, usually 32k x 8 (256k bits);
- Octal tri-state buffers, quad line drivers & receivers and so forth;
- Random crystals and occasionally a crystal oscillator,
- Miscellaneous but interesting devices such keyboard & mouse controllers, floppy disk controllers, real time clocks and so forth.
Identifying Parts
The hardest part of salvaging components from old computer motherboards would be identifying what you're looking at. Hence this guide!
Motorolla Chips
Motorolla in their infinite wisdom decided to leave off the first few numbers of each part number when printing their chips. So a F737 is actually a 54F- or 74F737 ("transparent octal tristate latch with 3-state outputs") and a F74 is actually a 74F74 ("dual D-type positive-edge triggered flip-flop").

How parts are labelled



Typical pin out for 28 pin 'skinny dip' cache modules

Useful Resources
- DataSheetArchive.com
- DigChip.com — Nice interface, need to register to view datasheets thought.
- AllDataSheet.com
- List of 7400 series ICs — to help track down devices from partial part numbers.
- And of course Google!