Onslaught is a CSS plugin that adds DODS style capture point game play with player classes, HL2 models/sounds, and a small pinch of Source Forts.
Linux and Windows binaries included.
You should also check out the custom maps available from the plugin's website.
More info, screenshots, and a download are on the plugin's site, hosted by SteamFriends, at http://onslaught.steamfriends.com/
If anyone would like to put a video together showing the items in use, respawn generators spawning a player, and game play in action I'll post that to the site too.