I too got REALLY bored with all my songs on my iPod, so I've recently come into some awesome new workout songs:
The Postal Service - Such Great Heights
The Postal Service - Nothing Better (one of my current favs)
The Postal Service - Sleeping In (another of my current favs)
Justin Timberlake - My Love
Royksopp - Remind Me
Royksopp - So Easy
Christina Aguilera - Candyman
Omarion- Ice Box
Black Eyed Peas - Don't Phunk With My Heart
Outkast - Bombs Over Baghdad
Skillet - Comatose (actually pretty much the entire Comatose album is fantastic)
That's just some of my new music, if you want me to go into my old music I have some good workout songs there as well (like the entire "Movin' Out" broadway soundtrack is fantastic for working out, Cake - The Distance, Emery - So Cold I Could See My Breath etc. etc.).