I'm not sure where to start adding to this, since I've bought so much in the last month. But I did get another "non-working" Titanium PowerBook for $12.99 that turned out to not only be nearly mint, but also only need to have its PRAM battery unplugged for it to start right up. I don't really need another one of these, but it looked so much nicer than my others that I couldn't resist at that price. It's also one of the earlier models (400MHz), which I didn't have.
I got a PowerBook 1400c for $30 after getting a partial refund due to one of the RAM expansion boards being bad. I really like this machine, even if it is super heavy.
I got several iBook clamshells relatively cheaply (the cheapest was $40 shipped), and have now gotten fairly adept at taking them apart. I've replaced three noisy/failing original hard disks with SSDs or modern disks, and resoldered one power connector that had to be held at a certain angle to work. I also took two Tangerine iBooks with various faults (including a smashed screen on one) and combined them into one nice version with the best parts from both. I also finally found someone selling modern iBook clamshell batteries that wasn't charging a fortune for them (the only seller on eBay who carries them wants around $200 apiece!) The one I ordered hasn't arrived yet, though, so we'll see how it is.
I got a G4 iMac in very nice shape for less than $50 shipped. I've never owned one of these, but love the design. I like it a lot better than the white iMacs that followed it (which I did own).
I also got a "for parts" Wallstreet PowerBook G3 for $20. It wouldn't turn on, but I was able to resolder the power connector and get it working. Unfortunately, it had been dropped and the screen was damaged. Strangely, aside from some lines of dead pixels on the far right side, the screen looked pretty good, but the colors were inverted. I was able to download CloseView for MacOS 9 and use the "white on black" option to sort of fix it, but the screen is still not great. A little too bad, since it was the 14" active matrix version.
I've also had some misadventures trying to repair 17" PowerBook G4s. The first one I bought just needed a new hard disk, but I stupidly managed to break the ribbon connector on the logic board where the top case connects (and I mean I broke it right off the board, which is way beyond my soldering skills to fix). Then I bought another one that wouldn't display anything on the screen, thinking that I could swap out the logic board. That appeared to work for about a day and then I started getting strange graphics glitches and freezes, before it finally stopped working altogether (I'm guessing the logic board was the problem to begin with, and not the screen itself as they had implied). Then due to some bad timing on some eBay "best offers" I ended up getting two more faulty 17 inchers. With one, the seller had tried to upgrade the hard disk but broke the same ribbon connector I had. Luckily, he had only broken the lock on the connector and not the connector itself, so I was able to fix that one. And the fourth one had a very weird screen defect where there were blotches all over the screen, some of which were much brighter than the rest of the screen. Luckily, I had two screens from my first two failed repairs, so I was able to fix that. For those of you counting, that means I now have two working 17" PowerBooks. I guess two out of four isn't too bad, right...?