O'Reilly's Velocity conference is the only generalized Web ops and performance conference out there. We really like it; you can go to various other conferences and have 10-20% of the content useful to you as a Web Admin, or you can go here and have most of it be relevant!
They've been doing some interim freebie Web conferences and there's one coming up. Check it out. They'll be talking about performance functionality in Google Webmaster Tools, mySQL, Show Slow, provisioning tools, and dynaTrace's new AJAX performance analysis tool.
O'Reilly Velocity Online Conference: "Speed and Stability"
Thursday, March 17; 9:00am PST