I'm a professional woman who rides to work regularly in everyday clothing. For me that usually means skirts or dresses and low heels or pressed khakis on more casual days. A few pointers:
1. No pencil skirts. If I want to wear one, I pack it in my pannier and wear a pair of running pants to get to my destination and then change when I arrive. This is a very quick change because I wear the rest of the outfit (blouse, blazer, tights, shoes, whatever) on the bike and just swap the pants for the skirt on arrival.
2. If a skirt is fuller and might blow around I clip a couple of binder clips to the hem to weigh it down. This works much better for me that the penny and rubber band trick that [MENTION=252435]RubeRad[/MENTION] mentioned.
3. Heels are fine on a bike because of where your foot naturally falls on the pedal. I'm not one to wear super high heels, so I can't speak to that, but a nice pump works fine. I can't see why a higher heel would be a problem.
4. I usually ride my loop frame when I'm in dresses and skirts, but a diamond frame works fine too. The only issue is that when you stop, the top tube pulls the skirt up. I'm often wearing tights underneath, so it doesn't really matter much to me. In the summer it's also not an issue because I wear TomboyX boxer briefs underneath, which look like bike shorts.
5. Speaking of the boxer briefs, these are awesome! They fit like unpadded bike shorts with a breathable, gusseted crotch. This may be more information than you wanted, but getting rid of the elastic around the leg holes of traditional women's briefs solves lots of saddle discomfort issues if your commute is longer than a few miles.
6. Merino wool is wonderful. It is breathable and warm. It doesn't get smelly if you sweat a bit. It layers beautifully. A typical winter outfit for me would consist of a base layer and merino wool turtle neck on top, a skirt with tights (two layers if it is very cold) on bottom, and a pair of boots. Add some gloves and a cardigan or blazer and a wind breaker, and I'm set for all but the very coldest days. If it is very cold, then the skirt goes in the pannier, and I wear a pair of black cross-country ski pants to the office and change when I arrive.
7. Hot days: There's no getting around this in the south where I live. I have found absolutely no way to ride in work clothes on hot days. In Memphis it'll get to triple digits with high humidity in the summer. On those days, I give up and ride in cycling specific clothes and all the work clothes go in the pannier. I clean up and change at the office. For me, that's typically between late May and mid-September. If I'm going to an off-site meeting where I won't have the privacy of my own office to use for cleaning up, I bring some witch hazel along. Spritzed on a damp wash cloth or paper towel, it works wonders.

Hope that helps.