I thought it might be the right time to start with gdb (again).
I found a couple of good videos at youtube and also a couple of good tutorials.
But i think this one is very interesting:
http://www.securitytube.net/video/5664
It is part 2 (part 1 is just logistics plus the note that you will need to compile with -g option or -ggdb).
Part 5 comes back to gdb (between that there is nm and strace and what not, interesting, but not if one is only interested in gdb).
He also mentions the video "Assembly Megaprimer for Linux" (i watched the first two, which mainly explain registers, they don't teach Assembly as a language. As far i can tell the stack and the heap are a big thing in C, they talk about it all the time).
I wrote a little summary of what i have learned yet (but it's only the very basics, you will find such anywhere on da web):
http://resident.dyndns.info/content/wordpress/?p=311
So, to make it short, i really like the videos from securitytube (in general, but i mean the ones about gdb) and hereby recommend them.