For Design topics, check out 99% Invisible (http://99percentinvisible.org/) and Design Details (http://www.designdetails.fm/).
I feel silly mentioning This American Life (http://www.thisamericanlife.org/) since it seems like everyone's heard of it, but the quality of the show is just so incredible I can't leave it out. There's the quality of TAL's storytelling and then there's everything else...
Radiolab is also incredible (http://www.radiolab.org/) for more technical/scientific topics, but it's definitely not specific to engineering/software.