I seem to remember back in the day talk of really good third-party drivers for Nvidia cards. I haven't owned an Nvidia card other than a geforce2; which drivers should I go with?
All I know of are the Omega drivers, although I can't say I haven't tried them for myself. However, from my experience, I have not had any problems using Nvidia's drivers. I used to have a 6600gt, and never ran into driver issues throughout its lifetime. I am currently using an 8800gt which I bought around the time of its release, and have not had any issues regarding its drivers since I bought it. The only notable problems I have heard of are issues regarding the control of fan speed, but have seen them fixed fairly quickly.
Personally I feel ATI's drivers have seem more issues than Nvidia lately. One example being the issues ATI faced with Battlefield Bad Company 2, causing extra long load times and other various problems.
Just use nvidia drivers. If you still play 1.6, make sure you replace the counter-strike openGL file with the new one that will come with your drivers.