Action Replays are still being sold at Codejunkies (http://us.codejunkies.com/Departments/PS2.aspx) for $24.99 but I have no experience with the site or the device.
Got mine today, had GTA3 + Vice City, Bloody Roar 3, Splinter Cell Pandora Tomorrow, Batman Begins, and Midnight Club 3 dub edition remix. Not bad for $12.
Yeah, I keep an eye out for Tales of the Abyss every so often, still not available but jumped from $32 to $44. I'm gonna stay away from Gamestop until their old prices return.
There are a few fames I've played multiple times. I've mostly replayed games with multiple endings such as Fallout 1&2, Arcanum, and Way of the Samurai 1-3.
I've also replayed games with awesome stories like the Final Fantasy series, the .hack series, etc.
*edit Woops I thought this was in...