There are Annual Passes & Premium Annual Passes:
Annual - Unlimited admission into all 4 parks for 365 days
Premium Annual - Unlimited admission into all 4 parks, water parks, Disney Quest & Pleasure Island for 365 days.
I don't the exact costs so check the Disney web site, however, the Premiums are about $120 more than the regular. Our premiums just expired. We are going to get more AP's, but are deciding whether to get the premiums or not. We actually still have unused water park days on some old hoppers so are not sure if we should spend the extra $120 per ticket (there are 5 of us). We don't do Pleasure Island & did Disney Quest once.
We absolutely LOVED having the AP. Used it during 2 Easter seasons (2 weeks each time) & went once in December for a week so we feel we got our monies' worth. We have decided that we will always go with the AP's just for the fact of the flexibility. You can go into a park for an hour at a time & not feel like you have "taken a day off of your ticket". We have gone to EPCOT to watch Illuminations & get dessert in France then walked around the Boardwalk to "work off dessert".
When we stayed at the Contemporary this past trip we went to MK in the morning, got FP's for Space Mountain, spent the day swimming & went back in to use our FP's & got an ice cream for the walk back to the Contemporary. Our kids loved it.
Only you know your budget, however, since getting the AP's, our trips have been 100% more enjoyable & less stressful. If you can swing it in your budget & will be returning for another trip within the year, then I say go for it.
Plus, you get a discount with the Disney Club card. I think $15 on regular & $20 on Premiums.