1999-2001 - Some sort of AGP Riva TNT that came with my PII. I didn't know much about tech back then and don't seem to have the card any more, so I don't know anything else about it.
2001-2005 - Upgraded the PII to a Radeon 7500 64MB AGP after I bought some game and it had problems due to the Riva TNT not fully supporting DirectX 7. My first experience in computer upgrading. A lovely card though, and it served me perfectly for the last four years I used the PII as a main system.
2005-2009 - Radeon Xpress 200 integrated graphics, used 128MB of system memory. I finally upgraded to an Athlon 64 tower, but money constraints left me with this crap. By 2008 it was mostly futile trying to play new games on it.
2009-2010 - Upgraded the Athlon 64 to a Geforce 8400GS 512MB PCIe. I had intended to just wait until I built a new machine, but for $25 I couldn't resist. Really quite a noticeable boost over the integrated even though it wasn't that powerful of a card. Since I was used to the integrated graphics, I mostly had older games on there and I was pretty satisfied with it as a result. I could even pump Half-Life 2 up to 1280x1024... it only took five years after its release for me to catch up!
2010-Now - XFX Radeon 5870 1GB PCIe, in my first real gaming tower. Set me back an insane amount, but even two years down the road it still runs everything on the best settings, at least with everything I've tried. I imagine it will serve me well for quite a long time.