On the iPhone I can speed up the playback of podcasts to 2x.
Is there a way to do the same in iTunes?
This is not natively possible in the Mac version of iTunes (nor Windows for the matter). You don’t mention if you have OS X or Windows. If you have the former, you have two choices:
1) If the podcast is an MP3 file, you can convert the file to an AAC file in iTunes (with an extension of m4a.) and then change the extension to m4b; the file becomes an audiobook which can be played faster if I am not mistaken.
2) Another alternative is to hear it in Quicktime, which has speed controls: Right click the file in iTunes and choose "Show In Finder”. Option-click the file (right click) and select “Open With…”, select QuickTime. Once in Quicktime option-click the "Accelerate" button to change the playback speed.
There is a Mac menubar app, that allows you to change the playback speed in iTunes. http://wetfish.de/
The way I did it was (windows 7 not sure how it would work on mac) copy and paste the podcast from itunes into my doccuments and then open the podcast in VLC (http://www.videolan.org/vlc/download-windows.html) i assume there is a download for Mac as well. VLC has speed controls and plays every type of file as far as im aware. Under the playback options it has a speed setting.
NB VLC also good for vidoes with out of sync A/V as has sync settings.
You can use Winamp or Windows Media Player and the Chronotron plugin to change tempo or pitch.