The only reason i learned about the hlp was that i used the prototype24 freespace2 torrent which is pretty much the longest living torrent i've ever seen(the first time i used the prototype24 fs2 torrent was back in 2004, and it's still got a good amount of seeders). Prototype24 text file included in the torrent had an extremely tiny reference to the hlp. Googled, hlp, arf-yarf-bark, found hlp and started my half a year long lurking session with my first post in the fsport forum.
Before all that, volitionwatch was kickass but i never even lurked on those boards, just always checked out the main site occasionally, it's cool to know that hlp and vwatch were both existing at one time in history(they're the big boys out of freespace sites).
