ADT recommendations, anyone?

[mightymark]

Hello all. I'm an undergraduate Computer Science Senior looking for interesting Data Structures to write about. I realize that this is more of a question of theory than practice, but I was wondering if anyone could provided suggestions. Anybody got some unconventional ADT that they've implemented in the past that might be fun for me to research. OR how about a good URL that might point me in the right direction? Any input will be greatly apppreciated. Thanks in advance, mark