The link Trax has provided only gives the possibility to anonymise/proxy web traffic, and possibly only HTTP traffic at that. This is very different to "scrambling your IP address", which isn't feasible for operations you're going to perform day to day.
There are general purpose proxies available but you'll find that the vast majority of them are either restricted access or extremely low performance due to high use.
Technically, I understand that they are legal but due to their nature "open proxies" are often denied access by more technically savvy and/or paranoid administrators because the nature of the traffic that goes through them is more dubious than usual.
If you're looking for secure communications you need to consider encrypted communication (e.g. SSH, HTTPS, SFTP, etc). If you're looking to "hide" yourself on the 'net you should consider more advanced firewalls that, among other things, refuse to return ICMP responses (i.e. you can't ping your machine) or software such as PeerGuardian with an appropriately chosen access control list.