SIGIR is pretty much THE IR conference of the year. I didn't go this year, but Greg Linden did and has extensive coverage of the most important papers presented this year over at his blog.
- "ResIn: A Combination of Results Caching and Index Pruning for High-performance Web Search Engines"
- "To Personalize or Not to Personalize: Modeling Queries with Variation in User Intent"
- "A User Browsing Model to Predict Search Engine Click Data from Past Observations"
Well worth a read, seeing as these ideas form the future of information retrieval.