The home we stayed in was actually on Holy Island, which is a much small island off the main island of Anglesey. The principal town on Holy Island is Holyhead, which is large enough to have all the shops and services you might need. It is also the ferry terminal for the Irish Ferries, which cross to a port just south of Dublin.
Holy Island has its own charms--it features gentle, sandy beaches as well as lots of wild, rocky coastline with lots of scenic views. The entire coast has been designated a protected area for marine life, and you can see many rare birds as well as seals. For the history buff, there are stone circles and henges--remnants of the Bronze Age peoples that inhabited this island eons ago.
If you want to take the ferry to Ireland, you have several options. There is a fast hovercraft ferry that makes the trip in just under two hours. The slower cruise ferry takes 3 hours and 15 minutes to reach the other side. The best fare available is a Wednesday-only day fare. If you want to stay in Ireland longer, it will cost you more. See the Irish Ferries web site at www.irishferries.ie for up-to-date timetables and fares.