The Astropulse and BOINC beta tests are underway. Currently this is a closed beta test, but some information can be found at
http://maggie.ssl.berkeley.edu/ap/index.php
Right now that page is not loading, but it is a valid URL. If you can't load it try again later.
It sounds as thought they may expand the closed beta tests shortly. Win, Mac and *nix clients look to be available. (all are CLI, though I think I saw where a Win client with rough graphics is available.) Clients can be downloaded, but it is not currently possible to setup an account, until the BETA test expands.