I run proxies. I imagine it wouldn't be too difficult to intercept login data, though I haven't really looked into it. If you want to use a proxy run by a member of the Blitz community, check out one of my sites at Divoxa.com .
In addition to normal http proxies, there are also https proxies which transfer information in a secure form. Whether this would prevent the operator from intercepting login data, I don't know. One https proxy that I know of is Proxify.com . You can find more listed at Proxy.org .
If you have access to shared webhosting or better with php support, you could set up your own proxy site. Visit the forums at Proxy.org to find scripts. Generally, you'll just need to upload the proxy script and you're good to go. Bear in mind that proxies use a lot of system resources, so if you set one up on shared hosting, make sure that it is not used by too many other people or your account will get shut down.
EDIT:
I found the info quoted below on the Surrogofier proxy script site at
http://bcable.net/project.php?surrogafier .
DO NOT USE THIS PROXY AS OF NOW TO ACCESS ANY SENSITIVE INFORMATION, INCLUDING BUT NOT LIMITED TO CREDIT CARD INFORMATION, SOCIAL SECURITY NUMBERS, SENSITIVE PASSWORDS, AND OTHER SIMILAR THINGS! Currently, SSL/TLS is supported through just entering a URL in the field. BEWARE: This does NOT secure your connection to the proxy server as of yet, only the connection from the proxy server to the web server the request is going to! This might create a false sense of security for some people, as your passwords are being passed openly without encryption through the Internet.