Voice Advice?

(Or should that be "advoice"?) I love using different character voices at the table in my tabletop roleplaying games. This technique helps differentiate characters, provide atmosphere, and separate what I'm doing as the GM (or player) from what the character(s) I control are doing. However, I've run into a problem: Keeping track of the voices I've used. This is especially hard in a larger or longer-running campaign. As a result, after a while a lot of my characters end up as BBC-drama-reject vague intellectuals (insert your own conclusions about my default personality here).

I feel like there should be a better way to keep it straight, but I haven't found a magic bullet in that regard. I've tried to jot down notes to myself ("scatter-brained Humphrey Bogart" or "goth-tinged weather announcer"), and that'll often get me close. If I'm feeling really inspired, I might include a typical quote or bit of dialogue from them, to find the character and get back in the mood. I feel like there might be a technological solution, but – if so – I haven't discovered one that's quick and easy enough for my purposes.

This half-baked idea is provided as-is, in case any of you all have found a method to make the process easier; if so, it might make good conversation fodder on the forums.

-- Steven Marsh