Finger the kernel.org finger server to get current kernel versions:

$ finger @finger.kernel.org
[zeus-pub.kernel.org]
Trying 204.152.191.5...
The latest stable version of the Linux kernel is:           2.6.13.1
The latest snapshot for the stable Linux kernel tree is:    2.6.13-git9
The latest 2.4 version of the Linux kernel is:              2.4.31
The latest prepatch for the 2.4 Linux kernel tree is:       2.4.32-pre3
The latest 2.2 version of the Linux kernel is:              2.2.26
The latest prepatch for the 2.2 Linux kernel tree is:       2.2.27-rc2
The latest 2.0 version of the Linux kernel is:              2.0.40
The latest -ac patch to the stable Linux kernels is:        2.6.11-ac7
The latest -mm patch to the stable Linux kernels is:        2.6.13-mm2