Himeji is famous for one thing: Himeijei castle. Unfortunately the castle is under reconstruction until 2015 and you can’t enter it.
Besides the castle there really is not so much to see there. I would recommend going to the castle as a stop-over when you travel from the Kansai region (Kobe/Osaka/Kyoto) to Tokyo.
You can store your gear in a coin locker in the station for 400-600 yen. The walk to the castle is about 2 km. Visiting the castle takes about an hour. If you go to the castle they will try to sell you a combined ticket to the castle and a nearby zen garden. This might sound enticing but I found the zen garden to be a bit of a dissapointment after seeing the beautiful zen gardens in Kyoto.