How to increase volume of podcasts for listening on speakerphone?

The podcasts I load onto my cell phone (droid) are not quite loud enough for me to hear on speakerphone while driving. I’ve been using earphones, but I don’t like using them while I drive. I want to hear it through the speakerphone. I tried using an FM radio transmitter, but it doesn’t work well on my commute because of bad reception in my area–I miss large portions while having to switch channels constantly. I can hear callers loud and clear on my speakerphone, just not podcasts. Is there any way to increase the volume of the podcast before I load it into the phone?

I like MP3Gain. It’s purpose is to make all your MP3s have the same volume, but, since you set that volume, it should work for what you want, too. And it’s opensource, and I always promote opensource software that works.