Tor 0.4.0.4-rc is the first release candidate in its series; it fixes several bugs from earlier versions, including some that had affected stability, and one that prevented relays from working with NSS.
Tor 0.2.5.7-rc fixes several regressions from earlier in the 0.2.5.x release series, and some long-standing bugs related to ORPort reachability testing and failure to send CREATE cells.