Notable local rides staying on tarmac, but avoiding busy main roads, are:
Gallanach loop (7 km; start Oban)
Lismore + Sustrans cycle path loop (47 km; 2 ferries; start Oban ferry terminal)
Mull North loop (103 km; ferry to/from Craignur; good camping at Calgary Bay)
Mull Central loop (77 km; ferry to/from Craignure; good camping on shores of Loch na Keal)
Loch Creran loop (cycle path from Benderloch)
Benderloch - Barcaldine - Glen Salach
Oban Cyle Sportive routes (86 and 140 km; http://obansportive.co.uk/)
The routes on Mull and Lismore are shown on the map below.