There are lots of very useful components on computer parts. After all, they are all made of electronic components. I have computer parts that date back to 1992, and every now and then I destroy them just to get the parts I need.
From motherboards I get: headers, jumpers, voltage regulators, op-amps, serial EEPROM, CR2032 battery holders, crystals (specially the nicest 32.768kHz xtals), a few capacitors, inductors
From really old modems (ISA bus): 5V relays, speakers, headers, capacitors
From PSUs: fans, capacitors, resistors, op amps, cool ribs, MOSFETs, diodes, wires
Basically everything can be repurposed and used in smaller projects. I've been doing that quite a lot.
LAst night I was desoldering an Intel D845GVSR motherboard, and there were a few LM317 (voltage regulator), LM358 (op amps), several headers, and several 8-128kbit serial EEPROMS, plus a few other goodies. The problem with Intel motherboards, however, is that they are a lot harder to desolder than any other brand. Out of the 40+ through-hole capacitors on the motherboard, only about 5-6 have been removed without damage.
That is not to mention that doing this is a lot more environment-friendly than just trashing the parts. Anything we're reusing is worthwhile the time and is less not-biodegradable stuff that is thrown into nature.