redline, bianchi, soma, and surly have some pretty small frames, and the redline and bianchi are pretty short and are available as complete bikes. redline has the conquest and conquest sport which are affordable. the bianchi has the axis which is shorter but a little more. I'd start with those. although the soma/surly lists the smallest size (42), don't be fooled - it's quite long - 52+ cm top tube. the bianchi and redline are 50 and 51 cm, respectively.
My wife is actually looking to get rid of her 2007 Trek XO2 with full Sram Rival components and Reynolds Alta comp wheels. Bontrager Race lite handlebars/stem, and X-lite seatpost. TT is 51.5 and she only has ridden the bike for about 60 miles total (3 rides). She doesn't want to keep both a road bike and a 'cross bike, so she wants to sell this. Color is brushed silver and is absolutely in like-new condition. E-mail me at jb1883us at yahoo dot com if you're interested!
I have a 52 CM Gunnar Crosshairs for sale
dark blue in color. Waxed and polished regularly.
retails for 800 new.
I would for the right price, throw in the King Headset, a set of DA Cranks + BB, ultegra rear derail and a thompson seatpost.
let me know, taking pics tonight.
mtbwrx AT gmail dot com