For up to date information on how to reach Islay:

By Ferry
Caledonian MacBrayne operate the two hour crossing which runs twice daily throughout the year, once on Sundays, with additional sailings during the summer season. 
For details of timetables and to make bookings telephone: +44 (0)800 066 5000 (Gourock)
Alternatively: +44 (0)188 073 0253 (Kennacraig), +44 (0)189 684 0620 or +44 (0)149 630 2209 (Port Ellen). 
Timetable and booking are also available online at 

By Air
Loganair, on behalf of Flybe, run a 40 minute daily scheduled service, from Glasgow Airport GLA to Islay ILY. Monday to Friday in the morning and afternoon all year round, Sat and Sun there is single daily fight. The Summer schedule sees a significant increase in frequency of flights. Please check with the airline: British Airways has a codeshare agreement flights to/from London and can be booked through them:  
Flybe +44 (0)139 226 8513
Islay Airport +44 (0)1496 302 022
British Airways +44 (0)844 493 0777, 0191 4907901, 0800 123111

Hire cars
Hire cars can be awaiting you at Islay’s airport, a 15 minute drive away on the road to Bowmore.
phone :01496 810544

By Bus to Kennacraig
Scottish City Link operate a bus service, route 926, from Buchanan Street in Glasgow to Kennacraig which links with ferry arrivals and departures.
Phone: +44 (0) 0871 266 33 33

A few excellent resources for planning your trip are and where you will find lots of information about the island, activities and events.