That would be a long list. It's better to enumerate the reasons why you should avoid certain clearnet web sites over Tor, and you can apply that logic to any web site you come across. 1. Don't log into any web site that you have previously logged into over clearnet. You will link your anonymous identity to your real identity. 2. Don't log into any web site that doesn't use SSL. The exit node can sniff your account credentials. It can also link you to other sites that you are browsing at the same time, because all those TCP streams are probably using the same circuit, which terminates at that exit node. 3. Don't log into or try to create an account on any financial web site over Tor. They are extremely paranoid and will probably flag your account. 4. You shouldn't write a lot of text on any web site where you have written a lot over clearnet. This forum has shown that stylometry is surprisingly easy for even amateurs to perform, as several people have been trivially identified through quirks in their writing style (see for example mtljohn and chaosforpeace). You run the risk of linking your anonymous and real identities. 5. Be extremely careful about posting photos. Metadata and identifying info photos have fucked a lot of people. 6. Don't enable Flash or Java on untrusted sites. If they require these plugins, that is extremely suspicious. YouTube is probably ok, but I wouldn't run Flash on any other site. I wouldn't run Java on any site, period. It is relatively safe to access the vast majority of sites as long as you don't log in or run Flash or Java. You can also disable JavaScript if you feel the need, although I think the threat from that is pretty low.