Not Updated For Current Season
This is my tank rammus build. I use this build to be the team initiator and also to take damage for your squishier teammates.
I find this build get enough life, armor, magic resist, and hp/5 to allow you to do all of your general tanking duties.
Seeing as 99% of ranked players are deathly afraid of rammus, and more generally all tanks. This build is more for normal games.
Ghost - The combination of ghost and powerball makes rammus an initiator in any lane at any time. Also allows you to get away from a fight gone bad.
Exhaust - with exhaust you can initiate team fights and pick out the squishy players and make sure to keep them in the range of your tremors and allows your teammates to finish the kills
if you want to remove either of these i would suggest...
Ignite - With rammus i find that it is easy to do damage to people, but difficult to finish the kill by yourself. Ignite would be a good way to finish kills on your own. I would yout his to replace exhaust.
Flash - This would be the last choice for summoner skills. If you really don't like two of the previous three skills, you can use flash to close gaps quicker and to stop people from leaving the area of your tremors.