libtorrent has set_piece_deadline() (docs) to indicate that you want a piece soon, it will affect the piece picker to prioritize that piece. You can also set a flag (alert_when_available) to indicate that you want a notification (alert) when the data is available, along with the buffer.
Something I've recently taken to doing is keeping one eye on the big torrent sites, just to see what's topping their download lists. I do so because it's illuminating to compare what people are willing to take differs from what people are willing to pay for. However, I thought it'll be an interesting exercise to be a little more rigorous than that. So, hitting the Mininova, I totaled all the separate torrents for each popular game and worked out a chart. This is a snapshot of PC gaming piracy, on a single torrent site, on a single day.
Methodology first. The numbers are total leechers. That is, number of people who are downloading from a torrent right now. Many of these - and the ones with the highest scores - have multiple torrents, which means it's possible that trying multiples at once to see which one gives the game first. However, since I've only added up the torrents from the PC games sections first page - smaller torrents on the second page with less than 293 leechers have been omitted. Also, these are only torrents on Mininova. It's the largest torrent site, but there's many, many more. Finally, I've counted bundled packs - where the Add ons are added to a torrent - as a single game for simplicity.
Secondly: The torrent kids will go wild for shooting stuff. In fact, any kind of shooting stuff. They don't even care if it's any good, as the sixth-position for the poorly-reviewed Turning Point demonstrates. While there's more strategic games there, what's also worth noting that the current big game - Sins of A Solar Empire - is absent, despite sitting #2 in the US retail charts. Which you may say is a cute demographic snapshot - though, I'll note, that while relatively few people are downloading it, despite the fact it has no copy protection, it's the second-most seeded torrent - even if no-one's taking, people seem determined to try and distribute it for some reason.
Thirdly, let's try a little really rough - if conservative - maths. Call of Duty 4 has been on sale for 113 days, assuming day zero piracy. A seven gig torrent, assuming a 100k download speed, takes just under a day to download. Assuming that the rate of downloads now is constant across those whole three and a bit months - which is incredibly conservative, of course, as it'd have been much higher upon release - that means 993496 copies will have been illegally downloaded via Mininova alone. Which is the sort of number that makes Infinity Ward sad.
Animetosho is an old-school kind of website but the information here to vast to share. The website has a huge library of anime series, and you can download the entire anime series with all the subtitles on torrent/magnet. You can download the file and all the subtitle files are included in the same file. 2b1af7f3a8