Blocking unwanted users from snooping your BitTorrent traffic is a great way to boost your privacy, but if your client requires you to find a blocklist (like the newest versions of Mac-favourite Transmission do), I-Blocklist will provide the best ones for you.
You don't want blocklists to be your only defence against BitTorrent snoopers, but it's always a good idea to have one up and running. Some clients configure it automatically for you, but others require you to type in a URL, and you may be wondering what to put there. I-Blocklist has the answer. Their main list page is a great place to start, as it's full of different blocklists you may want to use, depending on your downloading habits. For example, the "level1" list blocks anti-p2p companies or organisations (and is the list Transmission used to use by default), while the "spyware" list keeps you protected from users that have been known to use BitTorrent to spread malicious software.
Head to I-Blocklist's main list page below to check them out, and click on any given list for more info on what it blocks. To add it to your client or peerblocker software, just copy its "Update URL" and paste it into your client's URL box. If you want more information about a given list, I-Blocklist's forums are a good place to get more info.