UIE's Web App Summit 2008
This looks like a great conference for developers and designers alike. IMHO, developers who write any UI need to go to events like this, it's not just designers who create well designed applications--the whole team is involved. 
UIE describes the event: "Over the three days of this premier event, you'll meet the innovators and world-class designers behind today's most successful web apps and come away inspired to create amazing applications that will delight your users."
I have attended UIE's annual conference in Boston and local conferences by UIE speakers in Seattle--these folks not only know how to put together a conference, but the content is phenomenal. It's thought leading, real-life, practical and fun all rolled into one. I guarantee you that your outlook will be impacted after this event.
The summit is broken into 3 days:
Day 1: Full-day workshops - "You'll start your journey with our full-day workshops, designed to dive right into the in-depth expertise behind creating successful applications."
Day 2: Making a great web app design - "On Day 2, you'll explore what makes a great web app design, with the essentials for planning great designs."
Day 3: Implementing the Best Web Apps - "On Day 3, you'll wrap up the event learning how to implement the best web apps, uncovering how to successfully go from concept to a coded web application."
When: March 26-28
Where: Coronado Island, California
How much: $1,549
Full details: http://www.uie.com/events/web_app_summit/2008/