I've posted the method that we've developed several times in the past but I'll just give a brief description here. If anybody wants more details, I'll be happy to post them or send them via e-mail.
Basically each player has a chart with several categories on it and a blank line next to each one. The categories are things like Combat, Magic, Character, Goal, Sacrifice, Social, Skills, etc. (there are about 10 categories total). As the session progresses, the players will jot down very brief notes in the various categories when their character does something related to that category.
At the end of the session, they hand the sheets to the GM and he runs down the list, placing a (or sometimes more than one) "tic mark" next to each category the character has fulfilled. He then adds up the tic marks and multiplies them by a multiplier based on the character's level (I usually use 50+(current character level x 15)).
The benefits we've realized from this system are several:
First, we never have to calculate XP based on the tables in the DMG. Even more importantly, the game is not driven by combat. If a session goes by that was focused exclusively on political maneuvering or information gathering and contained no combat, we can still easily calculate XP using the same system.
It also has the added benefit of focusing the players on the game, their goals within the game and the roleplaying of their character. If they look at their XP sheet halfway through the session and see they've written nothing under Character or Goal, then they try to focus more on bringing their character's personality into the game and pursuing the personal and party goals of the character.
We've used this system for years (including back when we played Rolemaster, whose XP system is FAR more complicated and cumbersome than D&D's ever was) and it works great for our group.
