GeForce2 MX 400 (or maybe GTS, GF4 should lead to a price drop)
Radeon 7200 (not the 7000 which should be the VE)
You can't really go wrong with any card, especially moving from a TNT2.
Main rig: Athlon64 x2 4200+ | Asrock 939N68PV-GLAN | 4x512MB PC3200 | 120GB Seagate | Samsung DVDRW SH-S203D | VX550W PSU | WinXP Home SP3 / Ubuntu 7.10
Headache generator: K6-2 500 | FIC VA503+ | 2x64MB PC133 | Voodoo 3 2000 PCI | SB32 ISA PnP | 15,2MB IBM | Xubuntu 8.04 / DeLiLinux 0.7.2
Lappy: Compaq EVO N115 | Mobile Duron 1GHz | 384MB PC133 | VIA KM133 | Xubuntu 8.04
A big thanks to MS's Vista for making me look into Linux distros!