Burning CDs in Linux
Gui Tools
XCDroast
GUI: xcdroast. It's pretty self-explanatory. Sometimes it has issues though.
k3b
For the KDE-enabled, k3b is pretty nice.
Gnome - Write to Disc
In Gnome, using Nautilus for browsing files and directories, you can right-click on an .iso file and choose "Write to Disc..." Make sure you have a blank CD in the drive first.
Command line tools
cdrecord
xcdroast is really just a front-end for cdrecord. Debian patch their cdrecord. 2.6 kernels can be problematic. xcdroast doesn't seem to be happy on 2.6.9 kernels, so you're stuck with cdrecord anyway. Try:
cdrecord dev=/dev/hdc isoname.iso
It's usually easier if one is root whilst burning things.
Ubuntu is similar, except it wants
cdrecord driveropts=burnfree dev=/dev/hdc isoname.iso
on at least standard gradpc hardware.
(Meta-word: burncd)