...Let me ask you guys, whose games apparently don't have the problems mine do -- Do your players think about your game between sessions? Is it a good thing if they do? What sort of things are they thinking about? What might we wish they were thinking about instead?
Some level of between session mechanical thinking is desired, I think. I want players thinking about their next level, cool spells, etc. But I don't want them thinking about it to the exclusion of other things, and would prefer to engage them with continued play. In the game I'm presently running, I've opted to use email to keep that engagement level high.
Some things I do (and based on player feedback they've been successful):
* Take care of "montage scene" material via email. Creating, researching, identifying, bardic lor-ing (ran out if "ings" there, I guess) - they are all taken care of away from the table if I can manage it.
* Dangle plot hooks away from the table, and encourage people to talk in between session. If you end while the PCs are in town, send the players messages over email (or wiki, or forum, or what-have you) that the characters are approached by a messenger / have a letter waiting for them / hit them with local news or events. One time, while the PCs came back to town after an adventure, we ended the session with them coming back to see that they had been levied a fine on their house while they were away. They talked about it all week.
* Ending on a cliffhanger - especially a "big reveal." That's been the thing which as worked the best, I think. It generates speculation, planning, etc.