I love 'cross bikes just for the flexibility - you can run all sizes of tire, from skinny 23s to beefy 45s in some cases (Surlys -- and still have fenders!!!). The disadvantage of going with a cyclocross bike is that there no women specific models from major manufacturers -- though since people usually get a size down than they ride in road bikes, the top tube is then also shorter.

I suggest trying a Bianchi Volpe and a Surly Crosscheck, which have a relatively short and long toptube, respectively. My only bike for a long time was a Bianchi Castro Valley, a Volpe built up as a commuter bike (generator hub and fenders). True touring geometries are also great, comfortable road bikes -- usually a bit more upright position, and with a long wheelbase they are very steady on the road. All manufacturers have realized that most people are not 18 year old racers in aero positions -- they all have road bikes with more relaxed, upright, and longer wheelbase geometry: these are usually labeled something such as sport, endurance, comfort, coast-to-coast (for the Bianchi lovers).

And there are great deals on Craigslist and eBay; plus now is a great time to shop for bikes since the 2010 bikes are coming out, and the 2009 bikes are at steep discounts. I got my 2005 Bianchi Castro Valley in the summer of 2006 for $600 (vs $799 retail); 1998 Bianchi Eros off of Craigslist for $580; and 1996ish Bianchi Reparto Course Cyclocross for $610 on eBay; 2009 Novara Carema for $400 at the REI scratch and dent sale (42 cm bike returned because the person didn't like the ride -- smart woman because it has 700c wheels, so the geometry forward of the crank is actually a tad longer than my 52/53 cm unisex bikes -- but it makes a great bike for SO with his short legs and long torso, and works okay as a guest bike for smaller riders -- the headset can be raised upwards = back).