Tower Defence fanatics would love to hear the news that Element TD 4.0 has released a BETA version of the game publicly.
Most, if not all TD afficionados has heard and played Element TD 3.0, being one of the most downloaded map alongside DoTA in epicwar.com.
A have not seen a Changelog as of now, but i'll post one soon as I find it.
Download links:
http://www.eletd.com/download-game.php
http://www.epicwar.com/maps/41814/
more info:
Element TD website