It's no problem adding tor and privoxy on Dapper. But it didn't work. If turn on Tor in Firefox by Tor button, every request just returned with "domain name not resolved". After taking a look of /var/log/tor/log, it says something about version too old. Well, that's very true according to this page:
So I added new source following that to apt/sources.list. Sure enough after upgrading tor works like a charm.