Full ap might not be the way to go but, you can still be tanky while having a good amount. Rylais is a great item on him (it works with his passive) and abyssal scepter provides an aura, mr and ap. Zhonya's hourglass would be a great item, but not if you are the only tank on the team (the active will get the enemies to attack your squishies and real casters instead of yourself). Cd reduction is very important.
I enjoy jungling/roaming with the new Alistar(atk spd marks, Arm pen quints, flat armor seals, flat cd glyphs), it's a lot of fun if you get some help at golem buff 1st level. I start with a point in heal. my items are usually cloth armor 5 health pots, or a dorans ring. I'm still learning how to play him this way, but most games I find it to be very effective. Even grabbing blue then going to lane is a good way to go. I'm still experimenting with the masteries, I go 9/0/21 now, but when i first started I went 9/21/0. I'm thinking that if I dropped some points into both utility and defense trees it would be a good balance. making sure to get the increased buff duration in utility.
Laning my starting items vary, most times I go red crystal and build it into heart of gold, or faerie charm, wait for 5 more gold then get cloth armor, or dorans ring. When I go back first I usually get my boots, a gold per 5 item (philo or hog), and an ap item( amp tomb, or blasting wand) which eventually will build into either rylais, abyssal or zhonyas. I try to stay in lane as long as I can, I max my heal first, as it is very mana efficient and keeps me and my teammate in lane. I make sure to have 1 point in each of my abilities at level 3 though.
A build I never tried yet but might be one to think about is spell vamp, would work great with his passive. Will of the ancients looks good, but I'm not so sure if an expensive item like hextech gunblade is worth it.