Looking around the web, I have found 2 ways of downloading torrents without a client, and in your browser:
1: Bitlet.org - This site uses Java to turn your browser into a bittorrent client. You can go to a torrent search engine like mininova to search your desired torrent file. To download the torrent file you choose, right click on the download torrent link, copy the link location (e.g. http://www.example.org/file.torrent) and then paste it in the input box at BitLet - the BitTorrent Applet. Then you have only to click on "Download torrent" button and that's it!
2: Btaccel is different than Bitlet based upon the fact that it downloads the torrent to their server, then you can be emailed when done and download the file off their servers.
The disadvantage is you can't download torrents directly from private trackers, and an account is required to use this service.
however, you can use Btaccel to have it download a torrent when your computer is off, and download it directly from their servers from wherever.
hope it might come in handy someday