Actually, I read an little snippet of the November 08 Shonen Jump and they interviewed Tite Kubo. They asked him why he named it Bleach. So, not word for word, he said he originally was gonna make the characters use guns except for Rukia, so he was going to call it Snipe. But then he thought that swords were better, so Snipe wouldn't fit anymore. Then, since the shinigami wear black kimonos, he'd call it something related to that. Black would be a boring title, and the opposite, White, would also be a boring title. And finally, he called it Bleach to make the reader/viewer think of the color white.
There are many theories. the most logical and most popular one is to do with hair. Ichigo's is natrual colour, but he gets flack from the a lot of people for it. this is because, if you bleach black hair it turns an orange colour.
The title wasn't Bleach when Tite Kubo decided to draw a story about Shinigami. This was before he drew the one-shot manga that appeared in Akamaru Jump. The weapon wasn't a sword, but a scythe. Only Rukia had a scythe and the other characters used guns. At that point, the title was Snipe (as in "Sniper"). Right before he started drawing, he began to think that a sword would be better and realized he couldn't use Snipe as a title anymore. He began looking for a title that grasped the bigger picture. Shinigami are associated with the color black, but it would have been boring to use "black." "White," on the other hand, can suggest black as a complementary color. So Tite Kubo chose "bleach" to evoke the impression of the color white. ^.^