I've started riding a bike into work (maily because the underground is not a pleasant experience during the summer, that and I'm starting to get a belly
)
I ride on the roads, and don't use the pavement (not only is it illegal but dangerous) that being said a number of things do annoy me;
Cars parked in cycle lanes, all you drivers whinge that if there is a cycle lane then cyclists should use it (yes I also drive but try not to be so inconsiderate) yet most cycle lanes have cars parked in them.
Cars stuck in traffic seem to have the attitude if I'm stuck here you should be as well, and don't leave much of a gap for cyclists (or motorcyclists) to get through. It's not as if it'll make any difference to how long they spend in traffic. (Admittedly it may mean they can't accellerate and brake harshly to catch up to the car in front which has moved forwards one car length.)
Pededstrians at crossings just walikng over regardless of the lights and just expect you to stop for them (I'm talking about when the light is green for the cyclist and the pedestrians just wander into the road expecting you to wait)
All road users could do with being more considerate (that includes cyclists, who I constantly see jumping lights)