Thunderstone: edit: Also how can I tell if I page has been SSL stripped?
SSL Stripper works in two ways. It can try replacing https addresses with the equivalent http and it will show in your browser, so be aware of how your browser indicates an encrypted webpage (address starting with https plus a padlock icon somewhere, which should provide certificate/encryption details when clicked).
Another technique SSL Stripper can try is, similar to phishing, swapping the https URL you requested with a different, but similar-looking, https domain controlled by the attacker and signed with a valid certificate. Just as with phishing, the domain name should be visible if you check properly.
Since these techniques involve modifying HTTP initially, you can protect yourself by creating bookmarks/favourites for your key financial sites' https login pages and using those rather than clicking on any http webpage links.
Moxie Marlinspike's PDF
Defeating SSL has more on this.
Just to clarify - this isn't a Tor-specific vulnerability, it can happen whether you use Tor or not and Tor will prevent this happening in some cases (e.g. if your ISP or their network provider tried this stunt). However I have (once) come across an attempt to degrade encryption (to SSL v2) which my browser (Opera) reported as an error. So treat any certificate error messages with extreme caution (at least, switch exit node and try again).
Thunderstone: Do you have any recommendations for interesting sites to check? Basically, whatever you feel like sharing.
edit; Even with the Torbundle, should I still get the Tor button anyway?
The Tor bundle should include the Tor button plugin. To test that Tor is working try lookup sites like
ShowMyIP. To review your traceability, check EFF's
Panopticlick page (Tor alone won't affect this, but TorButton and other Firefox plugins should). To see what information your browser discloses generally, try
BrowserSpy, Privacy.net's
Analyze Your Internet Connection or
Leader.ru's Investigation Report.