How do I get my Riva TNT video card to work in X?

The SVGA X server that ships with XFree 3.3.3.1 includes support for Riva TNT. So, you need to install XFree 3.3.3.1. RedHat users can find XFree 3.3.3.1 packages in the updates directory on most of RedHat's ftp mirrors (What and how you need to do to upgrade XFree on RH is explained in the RedHat FAQ!). Debian 2.1/2.2 users should be able to install XFree 3.3.3.1 from potato packages (If they exist!? Up to this date only unofficial packages have been released. The official packages that will make it into potato should not take too much time though).

If you are using other distributions you need to check with your distribution maker the availability of prepackaged XFree 3.3.3.1 . If you can't find the prepackaged XFree 3.3.3.1, the only way to get it (particularly if you use slackware) is to install original XFree86 distribution which can be found on ftp.xfree86.org and mirrors. You need not to install the whole distribution, just the SVGA X server and the configuration program of your choice (i.e. XF86Setup, xf86config).