Here is another good table for romanization:
Hepburn romanization (hebon-shiki (ヘボン式): http://www.sljfaq.org/w/Hepburn
This one is most popular among English speakers because it is based on pronunciation that English speakers can understand.
For comparison, here is a full chart of all four systems:
http://www.sljfaq.org/w/Full_table_of_romanization_systems
