On-Hashira festival is held every 6 years, and this year is the year. If you miss it this year, you can't see the fest until 2016. It is held this weekend (Apr. 2 - Apr. 4, 2010) and next weekend (Apr. 9 - Apr. 11, 2010)

The highlight of the fest is "Kiotoshi". You can see Kiotoshi from last time (6 years ago, 2004) in YouTube.
http://www.youtube.com/watch?v=sWnk6PVNSI8

Kiotoshi will be held at:

This weekend
10:00am Apr. 4
11:00am Apr. 4
12:00am Apr. 4
13:00am Apr. 4

Next weekend
13:00 Apr. 9
14:30 Apr. 9
16:00 Apr. 9
13:00 Apr. 10
15:00 Apr. 10
11:00 Apr. 11
13:00 Apr. 11
15:00 Apr. 11

If you want to see Kiotoshi in good position, you should buy reserved area ticket (probably sold out already), or arrive at venue before 7:00am.

Wow that is some crazy stuff. This up near Nagano? Whats the best way to get there?

The place is at Lake Suwa-ko near (just south of) Matsumoto, Nagano (pref). Nagano prefecture has 2 major cities. One is Nagano (city) which at north part of Nagano (pref), and the other is Matsumoto at the central part of Nagano (pref). Shinkansen station is at Nagano (city).

The best way is to drive, as public transportation there around Lake Suwa-ko isn't as good as it is here around Tokyo metro area, and time isn't good for trains. (You should arrive at venue by 7:00am)

If you don't drive, 2nd pick should be taking JR trains. Take JR Yokosuka line to Yokohama, change to Yokohama line to Hachioji, then take "Azusa" Limited Express to Shimo-Suwa. There are shuttle bus service between Shimo-Suwa area and festival place. The bus stop is about 500m south from Shimo-Suwa station. From Shimo-Suwa station, crowd direct to the same place so just follow and you can't miss it. You should arrive Shimo-Suwa station by 6:30am that means you can't depart at the same day from Yokosuka...