Just about any program can work with gmail, but I like to just use my browser. I found a
notifier program that I use. Ubuntu has it in the repositories and Arch has itin the AUR (if you don't use Arch don't worry if you don't understnad that). While I looked for the page for that I also came across
this. Don't know how well it works. I might check it out myself though
edit: should have looked more carefully at the second one there, it's only for windows