from www.nagios.org
Nagios 1.3 has been released to fix a few bugs present in the 1.2 release (Changelog). If you’ve been using the 1.x CVS code for a while, this release won’t bring anything new your way, but you should upgrade if you’re using the official 1.2 release from last year. You can download the 1.3 release here. ( nagios.org/download/ )
Luca
Edited ]
Devel relase 2.0b5 is out. 
Luca
From www.nagios.org:
Nagios 2.0b6 has been released to fix a few bugs present in the beta 5. At the current rate, version 2.0 should see a stable release before the year’s end.
Latest versions: 1.3 (stable), 2.0rc2 (dev)
New versions of NRPE (2.2) and NSCA (2.5) have been released. Each release fixes a number of bugs present in earlier versions. Its been a while since updates for these addons have been released, but they’re here now. (nagios.org/download/#addons)
Luca