You can access 4chan through Tor, now. It used to be blocked, but now only blocks posting.
Additionally, there is an HTTPSEverywhere definition (you have to specially get it from their website) that forces all the 4chan content through SSL to prevent snooping by exit nodes.
Download and place the file in the HTTPSEverywhereUserRules/ subdirectory in your Firefox profile directory. In Tor Browser bundle, the location for your profile is: {wherever you installed tbb}/Data/profile
When you're in TBB, navigate to http://4chan.org. If it doesn't switch to https automatically, then click the HTTPSEverywhere icon up in the corner, and make sure the 4chan.org rule is checked. Page should refresh, you should see that it is now https.
Additionally, there is an HTTPSEverywhere definition (you have to specially get it from their website) that forces all the 4chan content through SSL to prevent snooping by exit nodes.