Weekend in Madrid - What to do?

I'm off to Madrid later this month with Mrs Popester for our first weekend away without the kids.

I've read a couple of travel guides, but would be grateful for a BBS view of what is worth seeing and where is worth eating/drinking at. We are staying close to the Museco del Prado and intend to visit that early on Saturday. Otherwise, we have no plans. I've never eaten tapas outside of England and am looking forward to trying the real deal.

Thanks in advance...