In just a few hours your can see the botanical garden, which doesn't on the face of it sound very interesting except for it replicates ALL of Colombia's climates and it is well nice. It is also just under the El Dorado flight path so good for plane nerds too.
Botero Museum is fab and you can spend a couple of hours there
You could go up to Monserrate with your camera (I am going this afternoon)
Check out the guinea pig racing on the corner of la 7ª and Jiménez
Gold Museum you could do (closed Mondays) you could do but I think that is a bit dull.
(This is in the order that I would do them coolest first)