Bee,
As far as clothing goes, I don't think you need anything special for a commute that short. Something to bind your trouser legs at the ankle to keep them clean (it is getting hard to find a decent bike with a chainguard in North America) and winter gloves for cycling maybe. I used to commute in gloves that were quite warm when walking, but virtually worthless on the bike. I found a pair of lobster style (split mitten) gloves designed for cyclists for $20 on sale and never regretted spending that money.

I eventually got one of those neoprene face masks too, but my commute was at least 15 or 20 minutes each way and I tended to ride all over the place before I got home. The mask really helps if you have sinus pain though.

Just make sure you wear layers in the winter.

What everybody else said about lights and helmets too! <img src="/images/graemlins/cool.gif" alt="" />