How to get various kernel versions

[reader at newsguy.com]

This is probably available somewhere obvious but flopping around in
the ubuntu kernel section of the online documentation... I'm only
finding how to get the kernel sources I'm running.   

No indication of how to get other versions.

It suggests the apt-get commands using `uname -r' to get the kernel
version. 

Trying something like apt-cache search ^linux-image-2\.6

Only returns version 24 flavors.  So how can I discover what all
kernel versions are available?