Bicycle Mechanics - How to repair wobble on the rear wheel?

I've got an old Raleigh road bike. Recently I have noticed, that there is an odd sound comming from the rear of the bike when I input more power. The sound resembles a sound, which is made by not fully shifted gear, though the gear is in the right position. Oiling everything did not help.

I have noticed, that the rear wheel wobbles a little to the sides (a small diagram in , where red represents forks, bold black is a tyre and blue shows how the wheel wobbles).

http://img407.imageshack.us/img407/6158/bikejh5.jpg

has anybody suggestions what to do? I have never experienced problem like that. Thank you.

If the wheel can wobble from side to side when it is not spinning, then the axle cones need to be tightened slightly. If you mean that when you spin it, you can see the rim move closer to a brake pad at one point in the cycle and then away again, it means a section of the rim is "out of true" and a bike shop can make tiny adjustments to the spoke tension to straighten it.

If the bike tries to shift gears when you pedal hard, try oiling the deraileur cable where it passes under the bottom bracket (between the pedals).

Try sheldonbrown.com for more tips.

Is the wheel properly seated in the dropouts?

Is the wheel properly seated in the dropouts?

Yes, it is. Probably, the problem is with the axle. I will have to tighten up the cones, as described in #2. The wheel is quite true (I did trueing not so long ago)