I was just trying to think of sensible stops I remembered from the interminably long train journeys to and from London
Basingstoke, Winchester, Eastleigh, Southampton Airport Parkway, Southampton Central, Brockenhurst (change here for Lymington for the Isle of Wight,) erm, Hinton Admiral, New Milton, Pokesdown, Bournemouth, Parkstone, Poole, Hamworthy, Wareham, Wool, Moreton, Dorchester South, Upwey and Weymouth. Not all trains stop at all stations (which is a good thing.)
The Weymouth & Dorchester West line goes up to Bristol, but it's not exactly a commuter line. Scenic, though. Also the Exeter to Waterloo line, which is slower (and cheaper) than the Paddington route, goes through north Dorset. Gilingham (hard G, unlike Kent) and Sherborne, I think. People do commute that, but I think the Weymouth - Waterloo line would be better.