Travel pass, rail card? what to get?

Hi,
I am going to Tokyo for a year (volunteering at a Japanese high school)
I will obviously be using the public transport ALOT and I was wondering if there was a good rail card or travel pass which would give me either cheaper travel or easier travel around Tokyo ( just like the oyster card used around london).

also on a side note how widely accepted are Visa credit cards in Japan?

many thanks.

Commuter passes for specific routes provide cheaper travel. And prepaid cards such as Suica and Pasmo provide easier travel:
http://www.japan-guide.com/e/e2359_002.html

Thank you very much, you answered my question excatly.