Realplayer used to be a bit of a naff, advert-ridden music player for me, but the latest version has one feature on it that makes it a must.
Almost any vid that you watch on the net (including anything off youtube) can be downloaded to your hard drive at the click of a button. Just hover the mouse over the video and click a 'download this video' button. Really, really handy. Great for dling gigs, music videos or anything you like.