Are you looking for the best conference in evolutionary computation and nature computing? PPSN, International Conference on Parallel Problem Solving From Nature, is probably the answer. This conference, which will be held in Taormina (Italy, check the conf website for some nice pictures) in September 2012, has the peculiarity of having only poster sessions to make the discussion about the proposed works more intense (and effective) than usual conference talks.
I think that famous conferences (like IEEE ones and GECCO) are becoming just a way to be seen and publish works which otherwise would need at least one year to be published on computer science journals, but the possibility of meet potential collaborators is getting smaller, because these conferences are huge (>600 participants!) with a massive amount of parallel sessions (the last IEEE SSCI I attended started at 8.30 in the morning and there were each day 6-8 parallel sessions, see the conference schedule…). Check the PPSN 2012 website to know the publication deadlines and getting other important information.
Read the interesting editorial appeared on the Communications of ACM with the title “Where have all the workshops gone?” about the workshops disappear (and the north american Dagschull Envy!).