For anyone who is having trouble downloading from the main page at Spelunky World, here are some mirrors.
Derek's original site- contains from 1.0B up through current version and source, as well as a few other games.
http://derekyu.com/games/My own uploads I've posted at various times, for various people, then lost the post where I put the links.
Version 99.9-exe only (3.3mb)Version 1.0-exe only (2.9mb)Version 1.0B-exe only (2.9mb)1.1 Current release-full folder in zip file (9.5 mb)Note that the older versions are the exe alone. If you want to use one of them, (for the spike safety for instance

) and don't already have Spelunky, you'll need to download the current version first and replace the exe in there. If you choose to do this, I recommend moving it into a seperate file, or creating a new one in the Spelunky folder so you don't lose it.