A lot of the things which were reportedly happening turned out to be not much more than rumours. Several local authorities have sent groups of volunteers to hand out water etc, but because of logistical problems they have been very small groups, with places being filled up within hours of becoming available. Your best bet is to make a friend in your local city office and get them to keep you updated.
When larger-scale things come around, I'll be sure to post. For now, there are several things you can do, as well as donating food, baby supplies and blankets (most cities have at least one drop-off point for this kind of thing). For example, we found a website dedicated to sending socks to the needy (there's apparently a massive shortage). You can read about that here: http://jasonkelly.com/helpjapan/ This site accepts donations from all over the world, so it's a great idea to contact places of work/schools in your home countries to get a programme started.
I know this can be a bit frustrating for those of us who want to do real hands-on helping, but it's incredibly important stuff.