Is it the 5 or 10% over the counter stuff?
Small 1 liter (quart)?
Unless you have a septic system, it is normally safe enough to fill the tub with cold water 1/2 way, add, mix, drain, run the water for 5 minutes. One disclamer... some cities/counties have some concerns about doing this. http://www.takebackyourmeds.org/what-you-can-do/faqs
Ton of stuff you can use it for... Google... however, be careful of some of the suggested uses.
If you dilute it 1:1 (2%ish) you can use it to bleach your white t-shirts by soaking them in the solution... just keep your hands out.