For boomboxes, you gotta be real lucky and persistent.... Tampa area craigslist hardly ever has classics on it. I've found two worth looking at in the last four years. Ira has one, Ed has the other. LOL!
But, for camera gear and old stereo stuff.... Craigslist absolutely rules!
Just the other day I picked up an original Nikon 18-200mm VR lens with a Nikon D40x 10MP DSLR for $500. I was specifically hunting for a camera for my uncle, who enlisted my help when his 6MP Nikon D40 developed a serious problem with the shutter. He was quoted $225 for the repair of his and didn't want Nikon to get that money. He said he'd rather try to find a used upgrade for that price. Well, he got his wish in the upgrade to the D40x for $250 and was thrilled. As for the lens, I've wanted the 18-200mm FOREVER, but just couldn't justify that $600-$800 price for a new one when my other lenses were doing the job very well. But, now I've got one in hand, and once I sell off my 18-105mm for around $200 I will end up with a very inexpensive, but major upgrade.
Loving the new lens! It's so nice not to have to change lenses to shoot up to 200mm anymore. I can't tell you how many shots I've missed due to lens-swapping. Plus, the performance of the lens is better than I expected it to be. I definitely scored a sharp copy!
If a person really knows how to leverage their knowledge for certain things, you could make a killing buying from CL, and selling on eBay.... despite all of the bullshit fees. If I would have simply separated the lens and camera and flipped them on ebay, I could have realistically pocketed around $400.
:'-( 
and I've done it however there are many in my area doing the same thing so getting to the good buys is tough, you have to be johnny on the spot.