This is filed under “Not necessarily ‘Straight Dope’ material, but where else would one post it?”
For quite a while I’ve wondered what four letters can produce the most words when rearranged. I vote for: O P S T
Stop
Opts
Pots
Tops
Spot
Post
Not really that many when you consider there’s 24 different arrangements.
Anyone have the “correct” answer?
dave, when you consider that three of those are plurals . . . 
part
tarp
prat
art
tar
rat
pat
tap
apt
par
rap
at
You never said we had to stick to four-letter words:)
According to Anagrams of four letter words, the best answer so far is
EAST
EATS
ETAS (more than one eta, which is a Greek letter)
SATE
SEAT
SETA (a bristle)
TAES (not in my dictionaries)
TEAS
If you have an interest in wordplay, you may like A Collection of Word Oddities and Trivia