RobbieTunes

Well, new or used? What do you want them to do for you? Wheels, frames, psi makes a difference.

I've got a ton of tires here, have had them on/off lots of bikes.

Narrow:
see my post on the 700x20's.
Other than my Avocet K20 Criteriums in 700x20, I'm not a fan of 700x20.

700x23:
Specialized Mondo-nice high-mileage tire. Not a racer.
Specialized Armadillo-save the money and tow something to get the same feel. They feel slow, but they last.
Specialized All-Comp-Seems about the same as the Mondo.
Conti Ultra Gatorskins-seem wider than they are, but roll well and look cool.
Conti GP 3000 and 4000-I consider most of my tires vs. the 4000.
Conti Ultra/Super Sport/2000, all beaded. They feel exactly like Kenda Koncepts
Vittoria Rubino Pro Intrepid (Kevlar)-Equal to the 4000 but looks wider. Doesn't last like an Armadillo, but longer than a ProRace, for sure.
Hutchinson Equinox-cheapest I have, rolls as well as anything, lasts as long as a ProRace.
Hutchinson Fusion Comp-Good tire for the money, not as cheap as the Equinox, but harder and much better handling.
Michelin ProRace 2 and ProRace 3-Good performance, poor wear, 2's can be found cheap, 3's are high, race-oriented.
Tufo S 33 Pro tubular clincher-My favorite all-around tire for wear/price/comfort. The other drawbacks are a PITA.
Kenda Koncepts-I have two sets, both 650x23. They change a lot once they start to wear.
Panaracer Stradius Pro and Pro II-Look nice, don't last for beans. Rain grooves, though.

700x25's:
Vredestein Fortezza Tri-Comp 700x25's. If they didn't say 700x25, I'd have never thunk it.
After the Continental Attack/Force, the best tires I've ever had.

If you're buying new, I'd recommend the Continental GP 4000's or the Vredesteins, if you want to spend some money.
For value, the Hutchinson Equinox, but don't expect them to last as long as more expensive tires.

Used, I like the older beaded Continentals with the dark gumwalls. They are solid tires.