How to resolve I2C address clashes?
There is nothing built into I2C to do this, normally slave devices will have some externals pins that can be set to 0 or 1 to toggle a couple of the address bits to avoid this issue.  Alternatively I've dealt with a few manufacturers that have 4 or 5 part numbers for a part, the only difference being its I2C address.

Most devices have specific hardware that handles the I2C communication, that is the slave ACK is in hardware so you really can't hack around it.

As for the translation module, you could buy some $0.50 PIC's with 2 I2C buses and write some quick code to make them act as address translators i guess.