[MENTION=24234]kinem[/MENTION], I have been adding important encounters to the Adventure Log. So if you want a summary of key events, you can always go there.
Also, one thing I have included in each NPC's bio is a "First seen in-character" link so in case you don't remember when or where you met an NPC, you can go directly back to that post. In the future, I will update this with brief details about future encounters since that seems to be a highly requested feature. So the bottom lines of every NPC's bio will include a "first seen," then if the character was encountered a second time, "rescued so-and-so from such-and-such" or "negotiated contract about such-and-such" with a link. When I have time, I update the NPC bios with information the characters know about them, either through gossip which is well-known and you have probably heard or information they have personally given you. You might notice, for example, Cydrak's bio includes his quote that the Sandpoint Theater is the "jewel of Sandpoint."
I have also been adding links to them in their respective locations, where they can usually be found. In my mind, it is the duty of friendly NPCs to generally stay in one spot, or be conveniently at those locations whenever the players need them (unless something unfortunate or plot-related has happened to them). So, for the location entries in Sandpoint, I have started putting links to NPCs in their descriptions. The Sandpoint page, for example, will continue to be updated as your characters visit other places in town.
So, in summary, I will do my best to keep a running account of player interactions with NPCs.