I haven't built a reddit-like site myself, but I'll throw in my two-cents anyways: 1. Here's someone who has created an open-source reddit-like platform in PHP

I haven't built a reddit-like site myself, but I'll throw in my two-cents anyways: 1. Here's someone who has created an open-source reddit-like platform in PHP: http://101out.com/ http://101out.com/ http://101out.com/versions http://101out.com/versions Unfortunately, it looks like it's not quite released yet. If you want to write your own in Ruby on Rails, this plug-in might be useful: http://rateableplugin.rubyforge.org/ http://rateableplugin.rubyforge.org/ 2. Not sure at all about cost. For reference, the 101out.com guy said he built his website in 20 days: http://programming.reddit.com/info/1e3dk/comments http://programming.reddit.com/info/1e3dk/comments 3. No. As someone else mentioned, reddit uses the python framework web.py. This site uses an unreleased version of LISP: http://www.paulgraham.com/arc.html http://www.paulgraham.com/arc.html 4. Good luck. 5. You should check back on this site frequently because a lot of these issues get discussed here often. There seems to be a good mix of hackers and non-hackers.