Go into Mandriva Control Centre ('Configure Your Computer') Software Management section, click on the bit labelled 'Select from where software packages are downloaded...', then click 'Add'. You'll then get a pop-up asking if you want Official Updates or Distribution Sources - click Distribution Sources then take yer pick! It's generally recommended to choose the mirror closest to you, although in my experience some seem more reliable than others (e.g. if you're in the U.K. I'd definitely recommend Anorien).
Another way to do it is to go to http://easyurpmi.zarb.org/
& follow the instructions on the site. In fact do this anyway, as you'll then get all the PLF goodies too!
After you've done all that you'll find tons of funky new stuff. Enjoy!
(p.s. Ktorrent is a fine choice! Also look at Kaffeine media player & Abiword word processor...)