Puddinpop's pool software allows the server to choose between "connected" and "contributed" distribution methods. In contributed mode, it behaves somewhat like slush's pool: every hash you calculate is counted, and the block reward is split among everyone according to how many hashes they calculated. In connected mode, the block reward is spit among currently-connected nodes only, according to the hash/s that they were contributing at the time.

I wish puddinpop's server would become popular again. It's open-source and built in such a way that miners can actually see what the server is doing on the network side (you download the full temporary block). Unfortunately, running the server is CPU-intensive, and probably it could not sustain the number of miners that slush's pool has now.