Jason,
Check these sites:
http://www.cisco.com/en/US/tech/tk365/tk80/technologies_tech_note09186a0
0800c95bb.shtml
The BGP section of the past Nanog talks:
http://www.nanog.org/subjects.html
And from our weekly celebrity's site, http://www.freedman.net/ - BGP 101
and BGP102 under the tutorial section.
A Cisco Press book by Sam Halabi: "internet routing architectures",
ISBN: 1-56205-652-2.