Torrific isn't the first HTTP torrent downloader but it'll download any torrent file your throw at it, help you search for what you want via Google and do it all for free.
Torrific is pretty easy to use. If you've already got a URL to a torrent file, just paste it in to Torrific and click "Get". Alternatively, you can enter a torrent site if you want to browse for a particular torrent, or just enter a search term and Torrific will turn to Google to help you find what you want.
Once you've made your choice, Torrific will download the torrent for you and provide you with a HTTP when ready. If someone else has requested the same torrent in the last two weeks, and it's still hanging around in Torrific's cache, you won't have to wait at all.
Torrific is free to use, but a premium level of service is available for $US10/month if you're a little less patient and want to avoid waiting times for larger torrents.