The following links should give you a few ideas about day trips and things to do nearby.
Take a ferry trip out to Eigg Muck or Rum from Arisaig or Mallaig
Or take a trip to the remotest pub in the UK, The Old Forge on Knoydart
Visit Glenfinnan and the monument
Take a cruise down Loch Sheil
Buy fresh fish from the renowned Andy Race in Mallaig
Visit a nearby distillery
Some other useful local websites