VLDB
I was browsing the program from this year's VLDB. I noticed a few papers that I thought were interesting: "Getting Priorities Straight: Improving Linux Support for Database I/O" (PDF), which is worth a read -- the authors are apparently collaborating with MySQL AB to improve MySQL's performance under Linux, including modifying MySQL to use AIO. I also liked two papers (one by Microsoft and one by IBM) on XML integration / XQuery optimization issues.
