Burning Rubber Smell

I went on a road trip this weekend and minutes before i got home last night, i noticed the smell of burning rubber when I stopped at some traffic lights and again when i parked the car in my drive way. I drove to work this morning and smelt it again after parking up - I immediately felt the rims to see if they were hot, all 4 wheels were warm but wouldnt say they were too hot to touch!?
Also, im not sure if this is related but when driving on the freeway, i sometimes notice that my steering wheel shakes/vibrates...