For years I am the one who believe that IDM (Internet Download Manager) is the best parallel download solution. Using that IDM for everything including download videos from youtube and any other flv (automatic detection), downloads via rapidshare, megaupload, mediafire and more. So, with so many trusted years, I believe IDM is the one and only the best among all.
However for now, everything has changed. Despite of so active internal updates from IDM, found out JDownloader (free open source) promise me with some new features.
JDownloader has all in-build features similar to IDM with some interesting additions including downloading in multiple paralell streams, captcha recognition, automatical file extraction, allow link encryption pasting, and import CCF, RSDF and the new DLC files. The catch is, JDownloader was written/ constructed using Java.
JDownloder requires you to prior install Java Runtime Enviroment (jre/jdk) 1.5 or higher.
Video guide on how to use JDownloader so that you will have the whole idea about what you are up to by installing this freeware. A bit old but the whole raw idea is there.