Cheapest way of calling from Japan?

Just wondering.. to call from Ireland to Japan I found that using call credit works out cheap enough (about 4 hours for 30 Euro).. what's the cheapest way of calling from Japan to Europe? If anyone has the names of call credit they use that would be great! (not from an international phone but from a normal land line?) Any advice would be much appreciated!

You can get prepaid phonecards, or if you have an NTT phone, ask for the INTL rates of the various carriers. You actually have multiple carriers at a time, so there is no switching. Just dial their prefix, plus the number.

VOIP phones are a great way to go, though I don't know how proliferous they are. I called Osaka every day for a while from the states and didn't run up a bill at all.