We're fans of the Koss PortaPro on-ear headphones, which retail for around $35 online and have a folding headband. The RP-HT21s don't sound as good as the PortaPros, but their sound quality doesn't fall that short and they cost nearly $30 less.
If you're looking for a cheap pair of headphones for casual listening on the go or at the gym, the RP-HT21s, despite their generic looks, actually sound pretty decent and are fairly comfortable to wear. Sure, some people may think you swiped them from your last flight, but the good news is that if you leave them anywhere (or accidentally break them), they'll only cost you $5 to replace. There's something to be said for that.