Dan's cyclocross got me started on this. I have to say my perception of biking has really changed over the past two years. My bike list used to consist of a full-suspension mountain bike and my old hardtail as a backup. Now my list is a bit odder (is that a word?)
Niner s.i.r. 9 rigid 29'er, singlespeed
Surly 1 x 1 currently setup with cyclcross type tires and fixed gear for commuting and the towpath. It really wants a Brooks leather saddle and some funky bars like Mary's flipped upside down... we'll see.
A Klein Quantum road bike, first year on the road for me looking forward to it.
And I still have the old backup hardtail.
That's it for now... but I wouldn't be surprised if something like a fixed gear road bike were added to the experiment in the future or who knows maybe a full-sus bike again.
So what's in your line-up?