Generate Random Structures Like Ruins

If there is anyone experienced with generating blocks/structures that could help me, that would be awesome!
I'm preparing my server to change to a new map for the first 1.2 CraftBukkit RB.
We have decided that randomly generated artifacts in the landscape would be incredible.
I've seen a SSP mod with ruins and small dungeons with different rewards, that will scatter themselves across the landscape when the world generates.

I have never even tried anything like this before, and It's probably quite complicated and i was just wondering if anyone has some basic/advanced knowledge and would like to give me some advice or pointers, (code snippets are also welcome!).

Thanks guys!
~Phys.