Harping my own story, they get together at the end of The Becoming ...in:
The Unexpected Universe
http://spikeluver.com/SpuffyRealm/series.php?seriesid=8This story picks up at the end of Season 2, The Becoming 2 and goes off canon about half way through that episode.
Buffy has made a deal with Spike to defeat Angelus. It goes off canon when Buffy leaves Giles' flat after talking with Whistler about how to defeat Angelus.
Will Spike still help Buffy defeat Angelus when things go pear shaped? And what then? Where will their lives go from there?
You'll find familiar challenges for Buffy with unexpected results as Spike faces them with her. If you like a story with love, romance, sex, fights, angst, tears, laughter, marriage and babies then you're in the right place! I hope you enjoy it!