I have BeyondPod for my Android, which lets me speed up the playback 1.5 or 2 times normal speed. Is there any Windows Phone app that has this feature?
The built-in Windows Phone 8.1 Podcasts app supports this.
Beside the podcast artwork display, there is a grey "1.5x" label. Press this once to select it (it goes white) and playback runs at 1.5x speed; press it again and it switches to 2x speed. Press it once more to deactivate it (switches back to grey "1.5x").