Googler Bryan Horling recently was on a panel with Danny Sullivan at SMX and talked about personalized search. A few people (  ) posted notes on the session.
Not too much there, but one interesting tidbit is the way Google is thinking about personalization coming from three data sources, localization data (IP address or information in the history that indicates location), short-term history (specific information from immediately preceding searches), and long-term history (broad category interests and preferences summarized from months of history).
A couple examples were offered as well, such as a search for [jordans] showing the furniture store rather than Michael Jordan if the immediately preceding search was for [ethan allan], a search for [galaxy] showing LA Galaxy sports sites higher in the rankings if the searcher has a long-term history of looking at sports, and favoring web sites the searcher has seen in the past. Curiously, none of these examples worked as described when I tried them just now, but it is still interesting to think about it.
What I like best about what Bryan described is that the personalization is subtle, only doing minor reorderings. It uses the tidbits of additional information about your intent in your history to make it just a little bit quicker to find what you probably are seeking. It's a nice, low risk approach to experimenting with personalization, making only small changes that are likely to be helpful.