you can oxidize things with the peroxide. it works like permanganates, halates, perhalates, etc, but is not quite as powerful. if you want to make a crazy acid and i mean CRAZY (it's called pirhana bath), just add it (slowly) to sulfuric acid. the more conc the sulfuric the more crazy your solution will be. you get peroxymonosulfuric acid, which tears through flesh like pirahnas and acts as a good solvent and oxidizing agent.
to concentrate it, just freeze; water freezes at 0 celcius, while H2O2 freezes at -11 celcius.