Here's a list of Mod links in alphabetical order by game and mod name.

Mods

New Maps

Action Half-Life Beta 4 (57 MB) (Team or DM: Action movieish action! Realistic damage, bleeding, bandageing, limping)

Cold Ice (DM: new crazy powerful weapons)

Counter-Strike 1.1 Full (82.3 MB) (Team: $ based. Terrorist vs. SWAT. Rescue/guard the hostage, bomb/ defend, VIP protection/assination, and escape/prevent missions.)

Day of Defeat (Team: WW II-themed mod that is nearing completion. Hopefully it will be a good replacement for the defunked War in Europe)

DMPlus (DM: Weapon modifications, grappling hook, cloaking device, inferred goggles, and more)

Firearms 2.5 Full (72 MB) (Team: More war like than CS, lots of Weapons. Pick a class or make your own cusom one!)

FrontLine Force 1.3a (54.2MB) (Team: lot's of weapons kind of like Firearms)

Gangsta Wars (DM&Team: The four modes of play are Capture the stash, Gangbang, Protect the Don and Deathmatch)

Half-Life Jailbreak (Team: CTF like mod with, but when you are killed you got to the opposing jail till your team mates spring you and there aren't any flags...I guess it's more like CtOT...Caputre the Other Team.)

Holy Wars Beta1 (11 MB) (Team or DM: capture the halo, and go on a rampage! Everyone else tries to kill the guy with the halo.)

Natural-Selcection (97 MB) (Team: like Counter-Strike but with aliaens and Marines with a commander mode also!)

Navy Seals (Team: They have an alpha release out that works, but it's incredibly unstable at the moment, and they don't suggest playing online with it)

The Opera R1 Full (87.3 MB) (Team or DM: Hong Kong Action Movie style, diveing, rolling and akimbo weapons!)

Science & Industry (Team: Protect your NPC Scientists. Steal the other teams Scientists who research technologies for your team so you can have access to better weapons.)

Team Fortress Classic (Team: Half-Life version of the old school Quake mod Team Fortress) Included in the latest Half-Life Patch.

War In Europe Beta 3 (59 MB) (Team: production stoped)

Wasteland (DM: Post-apocalyptic mod inspired by Mad Max and the Fallout games)

Q3 Assimilation Beta 1 (2.8 MB) (Team?: ?.)

Q3 Assimilation 104 patch (304 KB)

Q3 Fortress Beta 1 (36.2 MB) (Team: Team Fortress for Quake 3.)

Q3 Fortress Server Side patch (176 KB)

Infiltration 2.75 (7.8 MB) (Team?: ?)

Lazy Matrix 2.5 (186 K) (Mutator: Can be used with any mod or UT match to add random Matrix slow-mo action to it.)

Minions of Destruction 2.0 (4.2 MB)

Monster Madness 201 (25.6 K) (Mutator: Add big monsters to any Mod or regular UT match.)

Tactical Ops Beta 2 (104 MB) (Team: $ based. Terrorist vs. SWAT. Rescue/guard the hostage.)