In my best pimping way, may I suggest that you start off with janedavitt's Running Scared, a great Wesley/Dawn fic noir with snark a-plenty, and some of the best cliffhangers EVER. Previous parts can be found at the link provided.
Not forgetting liz_marcs's magnum opus Living History, now nearly over. *sniff*
The ever amazing houses7177 has updated TWO of her stories : Courtly Behaviour and one I'd never seen before this week : Sweet Dreams are Made of These. Both highly recommended.
And last though not least, elementalv's Key's Watcher universe. The latest parts of which can be found here.
Go forth and feedback!