Is there any good flash video downloaders which allow you to download online videos in HD quality just like IDM does?
Orbit Downloader is good. Firefox and chrome plugins are also good.
AnyVideoConverter is good. or use Firefox with DownloadHelper Plugin.
you can use youtube downloader-hd as a desktop software or download helper as firefox add-on.
use downloadhelper addon for firefox or follow this trick
(you need to have java installed on ur pc)
Since u r using chrome, use this app https://chrome.google.com/webstore/detail/fvd-video-downloader to download flash videos ;)
some of the alternatives mentioned here are good. but i would also like to suggest some online options like keepvid.com, savevid.com, zamzar.com, etc.
Freemake Video Downloader -> http://www.freemake.com/free_video_downloader/
FVD Suite -> http://flashvideodownloader.org/fvd-suite/
Free Download Manager -> http://www.freedownloadmanager.org/
They are all excellent and absolutely free.
Free Download Manager
VDownloader – Really Easy Video Downloader Software (+ 20 Free PRO Accounts)
4K Video Downloader
You may also check this one - video grabber. A free alternative to IDM, No installation and ease of use, but it allows three times downloads at most everyday.