I still play CS:S quite a bit. If anyone else has played the GunGame mod, they can probably attest that with the right settings it's insanely fun. I have, for instance, dragged Woggy, into a game or two of it and he seemed to enjoy it. I would highly recommend it.
The idea is you start with a glock and each kill you get you move on to a slightly more powerful weapon until you're at the grenade and then the knife. You have to get a kill with the weapon for the level you're on (i.e. level 1 you need a glock kill to advance to USP) My personal favourite settings are deathmatch (makes it more hectic and less irritating when you die since there's no waiting about), 5 kills per level to advance and turbo mode on (when you get a kill with the correct weapon, the next one appears in your hands with full ammo, leading to rampages if you're on a roll).