Originally Posted by cyclezen

Very Late 90s and 2000s is a sweet spot for, all the building materials. Really, 'Brand' is not important, many great bikes out there, a lot depends on your personal taste and, of course, what geometry you might wish/need.
Patience and Craigslist will have you finding something - depending on where you live.
You'll need some knowledge about bikes, and the good stuff. What you don;t know, you can search and ask here.
Things I would avoid:
1. Square Taper - is still available, but in better bikes, it's for the 'Vintage' crowd.
2. I would also avoid anything using ISIS, OCTALINK or the Campy equivalent (name escapes me...). They were ok, but became problematic with extended use... Stay with any of the Modern crankset/BB combos which have the Crank spindle attached to the Drive side Crank - mostly bulletproof and great shifting.
3. 9 Speed was good, But 10 spd is awesome good, 1st gearing which could handle shifting under load an 'expected' good result. 10 spd also has the greatest variety of stuff available, especially gearing combinations (chainrings options and a vast range of cassettes).
4. Late 90's and newer should all be 'Threadless' stem, although the old school Quill Stem might sneak in... I would avoid Quill Stem bikes and any with 1" headtubes.
5. If you're a real 'trackie', you would know 'sewups/tubular' - avoid... stay with clincher wheels. Tubular are still common to very recent times, for racing, but they are finally having the nails put in their coffin (maybe...)
6. Wheels, complicated, some good, some not so good. Best to ask specifics here when you have some for consideration.
Good Luck, happy tire kicking ! Bike shopping is super great fun!
Ride On
Yuri