Lots of Warner Home Video cartoon sets hit on Sunday for $3 a pop (mainly Hanna-Barbera). The biggest jaw-dropper: every Big Lots I hit had at least 5 copies of the beautifully remastered Popeye volume 1 set (1933-1938). If you don't have it yet, it'll be the best fiver you ever broke at Big Lots.
Also sighted in the wild (from memory), starting with the cartoons:
*Dastardly and Muttley
*Josie and the Pussycats
*Perils of Penelope Pitstop
*several season sets of The Flintstones (reported by others, but not seen by me...apparently they're gone as fast as they're put out)
*At least one Superfriends set from the Zan and Jayna era
*Adventures of Superman (the 1950s live action one) season 3-4 (complete with a long-expired "movie cash" check to see Superman Returns in the theaters) And on that note...
*Lois and Clark: The New Adventures of Superman
*a three disc Larry King Live retrospective
*I also remember seeing Roots: The Next Generation, but I don't remember the price point.
There are also NFL (Superbowl) and NBA team retrospective sets that keep popping up (again, not seen by me). I know what a lot of these originally listed for...to get them for $3-6 now is amazing...and a little alarming.
There's a pretty comprehensive "field report" thread
at the DVD Talk Forum.