It depends on what you mean, if you just want a new IP from iBurst then reconnecting your modem or disconnecting from your router will give you a new IP.
For a totally different IP, not identifiable as iBurst, you can use any service with iBurst, it should all work fine, Torr being a good example.
No need to bother with Torr if you just want to fool Rapidshare into thinking you are a new user or something similar.