My league is just getting into our first offseason (started as a keeper last year) and we're using the 'standard' method of losing the pick a palyer was chosen in the year before. We're allowed 3 keepers, but only 1 RB. We've also added the wrinkle that we get to choose our draft position in the order of last year's finish.
I've found that it's been a pretty good system so far. Only 5 players chosen in the first 2 rounds last year are being kept mostly because people found better value with later keepers - I cut edge (1st rd) to keep j jones (8th). There were more trades at the deadline than ever as studs were swapped for keepers and kept people interested to the end.
We're all very active owners, so it makes sense for us to reward the guys draft well and scour the waiver wire all year. It's really made our league more competitive and a lot more fun.