I would suggest looking into reputable local pawn shops and mom-and-pop game stores if you have any where you live. This will also give you the chance to inspect the system first-hand before buying. I know that the local pawn shops and mom-and-pop game stores where I live will often have last-gen systems for less than most places (Gamestop for example).
Amazon Warehouse deals (used games and consoles). There's a thread in the video game deals section where members post good links to deals. You could find a nice bundle for around 120ish or less.
Also try Cowboom, an offshoot of Best Buy. Just be careful to read the descriptions as sometimes they sell consoles with missing cables or no controllers etc.
As far as used PS3 systems go for a good deal those, in my opinion, are your two best bets.
Both have good return policies too especially Amazon.
I was looking at this earlier for where I could find deals, and I just grabbed one off eBay and hope it gets sent for the rare instance something bad happens. Seems like a good deal, though. Probably the same with cowboom, but you get to ask the seller direct questions and I figure cowboom isn't as easy to ask directly. I figure cowboom just has a warehouse of them or something.