Alameda is pretty small and flat, so getting around is relatively easy. Biking is popular. There is a pretty good bus system, a number of taxi services, and of course one can drive or walk almost anywhere. OpenStreetMap has a pretty good map of Alameda - though it can always be improved.
To get on and off the island, there are 2 Ferries, 4 Bridges, and 2 Tunnels (or rather one pair of tunnels, one entering and one exiting at the same spot).
Driving directions
You drive, and you get here, or there.
Public transportation
AC Transit
For their website go to http://www.actransit.org/
BART
For their website go to www.bart.gov/
Airport
The closest airport is Oakland International (OAK) at http://www.flyoakland.com/