For many years, I've been lifting weights after biking from about October to May. Sometimes after a spin class or roller work in the winter, sometimes after a 2 hour ride in the spring. "Normal" recommendations for weights are either to do them before aerobics or not to do aerobics on the same day. I started lifting after aerobic work in my 20's after trying the normal recommendation and getting no improvement in my aerobic ability. I still got improvement in my lifting ability, in fact it didn't seem to damage my maxes at all once I got used to it. So that was just my experience for 40 years or so.
Now comes the Swedish School of Sport and Health Sciences with a November 2011 study which finds the science behind my experience:
I think that's a big deal.
The Oct. 2012 study I was looking for at the SSSHS, before I also ran across the above study of theirs, further validates doing an occasional second workout in a day, glycogen-depleted:
I've tried that, too, but recommend it only for the highly motivated, which I'm not sufficiently.