All power pollutes. ALL of it.
Coal - CO2 (climate change), ash, particulates, toxic heavy metals, the impact of mining it and associated safety risks.
Oil - CO2, all sorts of contaiminants, localised air pollution, spills, the impact of drilling for it. And of course the national security / military implications of oil.
Gas - CO2, NOx, methane leaks (climate change), the impact of drilling for it, risk of explosions etc. Long term, add in the national security / military aspects that presently apply to oil as small gas reserves are used up and the world increasingly relies on Russia and the Middle East for gas.
Nuclear (uranium) - A toxic waste legacy that will, in practical terms, be around forever. The impact of mining the stuff and the risk, however slight, of a catastrophic accident.
Hydro - Flooded valleys, impact on landscape etc, the inevitable reality of having to run transmission lines and roads through scenic areas to get to power stations.
Wind - Kills the birds, especially the larger ones (some of which are endangered). Plus basically all the same impacts as hydro apart from actually flooding anything.
Wood - So much has been said about forests and the environment already that there's not much to add apart from localised air pollution.
Solar - Clean in use maybe, but not so green once you consider all the materials (including wood and fossil fuels) that go into making a solar panel in the first place.
It all pollutes, all of it. All we get to choose is what form the pollution takes and where it ends up.
Personally, I prefer energy sources which do not carry the risk of anything truly catastrophic happening, that arent likely to start a war and where the environmental effects are at least known and quantifiable. In that context I'm not too worried about wood, wind, solar, hydro etc whilst coal and gas are the best of the remaining alternatives.
It's uranium and oil that have the potential to cause real trouble any moment...