The Japanese Red Cross site is really busy.
Anyway, this is the page about donation.
http://www.jrc.or.jp/contribution/l3/Vcms3_00002069.html義援金窓口1 郵便局・ゆうちょ銀行
口座記号番号 00140-8-507
口座加入者名 日本赤十字社 東北関東大震災義援金
取扱期間 平成23年3月14日（月）～平成23年9月30日（金）
※郵便局窓口での取り扱いの場合、振替手数料は免除されます。
※郵便窓口でお受取りいただきました半券（受領証）は、大切に保管してください。
※通信欄にお名前、ご住所、お電話番号を記載してください。
救援金窓口２
■ クレジットカード・コンビニエンスストア・Pay-easyによるご協力
詳しくは、こちらをご覧ください。
Basically there are two ways, deposit into their account in Japan Post Bank (without transfer fees), or online such as credit card.
I can arrange to deposit cash (in Yen) directly into their account. Direct deposit would eliminate possible exchange fee on credit card which could be quite a few percentages and other possible fee. And the amount can be precisely worked out before hand.
I trust the bitcoin community, I can deposit the money first, provide the bank transfer slip before accepting the bitcoin.
And we can work out an exchange rate were the community is comfortable with.
Apart from Japanese Red Cross, there are some other funds such as Yahoo Japan 緊急災害募金 Emergency Disaster funds.
http://bokin.yahoo.co.jp/donation/detail/1630001/index.htmlBut their are also donating to the Japanese Red Cross. So a direct deposit to the Japanese Red Cross seems to be the most reliable and convenient and "to the point".
Donation to the Japanese Red Cross can be as quickly as a consensus is reached here.