Anonymize.net: Providers of anonymous secured Internet access service where all traffic is routed through an encrypted VPN connection.
Anonymizer: Offers anonymous surfing, secure tunneling, dial-up, and anti-spyware software. Trial versions available.
beHidden.com: Offer 30mb of free anonymous transfer per day. Paid service available with no limits. Also offer anonymous email.
CECID: CECID (and its client FLACCID) are anonymisers that remove tracable information and bounce a request off several other clients in a decentralized P2P anonymisation network.
Domain Forte: Anonymous Web surfing via CGI proxy
Guardster.com: Anonymous web proxy, with additional features for subscribers.
Proxy Stealth Tests: These tests will allow you to check to see if your proxy is anonymous.
Somebody Anonymizer: Commercial service provides proxy, enhanced DNS, privacy protection, anonymous surfing, anonymous mailing and anti-censorship services.
the-Cloak: Anonymizing proxy with option to remove Java, JavaScript, and block cookies and ads. Requires JavaScript. Pay service offers more bandwidth than free version.