The fifth alpha release of Seaside 3.0 is out. Check out the release announcement. It's looking like Cincom, Instantiations, and GemStone will all include this version in their next upcoming releases; Pharo users can use the Seaside Builder to generate a load script. Squeak users will probably have success using the Builder as well, but we are looking for one or more people to actively test and maintain a Squeak port. Get in touch if you're interested.
We're expecting this to be the final alpha release, so now is the time to actually send in any bug reports you've been sitting on.