It's been a long time coming, but the Natural Selection people have done it again with the release of Version 3.0 of the highly rated Half-Life modification.
Natural Selection has enjoyed a reputation as possibly the most unique Half-Life mod around, and certainly generates a buzz wherever it goes. Version 3.0 is the latest and greatest, boasting many bugfixes, awe-inspiring new maps, new gameplay, improved visuals, in fact all around improvements. If you're a seasoned NS player then get it now (be careful of the new cloaking), if you're new to NS then get it now (and be careful of cloaked aliens).
Have fun guys!