Some information regarding another of those popular ever lasting Half Life mods.

Over at Computer Games Magazine they have a small interview with the mods creator, Charlie Cleveland who talks about version v3.0 of the mod, and also a few comments regarding the future HL2/Source port.

Some of the bigger gameplay changes include: innate alien regeneration (so aliens don't have to keep running back to the hive, and to reduce dependence on defense chambers), a big rework of cloaking (to make sensory a viable first chamber), cheaper cat-packs, free alien upgrades, and decreasing spawn times in large games. NS plays much better in large games now, and generally allows much more of the upgrades and technology to be useful. This is the first version we were able to take a lot more player feedback into account and we're really happy to give players what they asked for (but no flamethrower...yet).

Full Natural Selection v3.0 Interview