The War and Peace Museum (ph 01631 570007) always seemed to be teetering on the brink of insolvency but it is now more secure and worth a visit - and a donation because it is free and entirely volunteer run - if for no other reason than to get an idea of how surprisingly important Oban was in the second world war, mostly as a base for antisubmarine flying boats (the museum features war rather more than peace). The volunteer staff seem mostly to be ex servicemen from that era, always keen to yarn about the old days - and very informative too, much better and of course more interactive than one of those audio machines that museums give you to talk you round the exhibits. And as volunteers they do come free, at least for as long as they remain standing (in the meantime someone should be and probably is recording their stories).
The Atlantis Leisure Centre has a good swimming pool to take the family to on a wet day. There is an adult 25 metre pool which is a bit cold (and has a flume), a toddlers pool which is a bit warm, and a bouldering wall.
There is a cinema for a wet day - the Phoenix. It rose from the ashes after it burnt down in the 1950s, closed in 2010 but in 2012 it reopened as a community owned arts venue. In 2013 a second screen was added. Terrific. Use it.
The Corran Halls hosts various groups and acts, and there is the Skipnnish Ceilidh House which may offer something more than tartanery of an evening - I don't know.
The Oban distillery is right in the middle of town and takes up a surprising amount of space behind the main street. It is not wildly interesting architecturally. Of course it does tours.
The most obvious feature from the sea is the late 19th Century Colosseum-like McCaig's Tower. Mr John Stuart McCaig died before it was completed and it has been left as it was then, best seen from afar, although close up it is rather tidier than it was, with good views across the bay, no litter and nice shrubs. There are steps up to it from the end of the road by the Skipnnish Ceilidh House. Interestingly, McCaig must have been some sort of pre-Keynsian because it is said that in part his idea was to provide work for local stonemasons in the winter.