Back in February, Valve released the source code for Team Fortress 2 (TF2) into the Source SDK, which allows modders to see how it all works and get their standalone mods onto Steam. But also, it allows them to fix up issues directly in Team Fortress 2.
If the fixes keep coming I might just get back into TF2. I first played it and got hooked through The Orange Box on the PS3 and then eventually on PC when i got a gaming laptop years later.