More ideas from my conversation with Joanna, someone I know who is contemplating recycling the components from her old road frame onto a cross/commuter frame:
The Competitive Cyclist fit calculator is a good place to start when trying to find the right size frame.
Measuring your existing bikes also helps. As a woman, you're going to want a shorter than average top tube. This is always a challenge for women looking for a cross bike since there aren't women specific cross bikes yet and a female specific frame tends to be built for shorter torsos.
Another tip - a pair of touring tires is probably good for a cross/commuter. Cyclocross tires are expensive and wear out quickly on pavement. Touring tires have a bit of tread and wear like iron.
Budget some money for frame building tools and expenses:
-bottom bracket tool
-headset installation (that's usually a job for a pro mechanic)
-a new set of cables and housing
-a new chain as your chainstay length may increase
-a new cassette to go with your new chain, budget cassettes are heavy but durable
-odds and ends like handlebar tape and cable donuts
-a set of good ball-end hex wrenches, don't rely on a multi-tool. Bondhus offers a lifetime warranty, I've used it, it's worth it.
-a cheap, maybe 2nd hand work stand. It will save your back! (this is something you can usually borrow)
Also, most assembly steps require grease. A tube of plain old grease from the auto parts store will be good enough. Get some latex or nitrile gloves, maybe some industrial q-tips.
Also, put the cell phone number of your favorite bike mechanic buddy on speed dial, to call when the going gets confusing.