Worthwhile Industry Trade Shows for Developers and Admins?

PacketMaster asks: "This year I attended JavaOne in San Francisco. Working for a company that uses Java as its primary programming platform, we thought this would be a good show to attend. While there were good nuggets of information gleaned from these shows, a lot of the talks were 'Today we're going to look at X and then show you how to implement it in {INSERT PRODUCT}.' Basically the whole show was a continuous Sun sales pitch! We're in budget planning time and we're discussing what shows we want to go to this year. What are some recommended shows that are actually useful for either programmers using open source applications like Linux and MySQL, the Java environment or systems administrators using Unix?" In today's belt-tightening economy, many companies don't have much money to waste on sending their employees to shows that will waste their time. What conventions and trade shows actually offer useful information rather than trying to indoctrinate their attendees on commercial products they may not want or need?