If you haven't been picking these up as they're announced, Amazon decided to finally give you a way to get all 25 with one click over at their 25 Days of Free page (amazon.com) - scroll down past the days to find the checkable list and "Buy selected song" button.
Oh, one more thing - if you're GIFTING MP3s, Amazon says that you can get $2 off with the code GIVEMP3S. Details about THAT over here.
Just wanted to let you know that I've got the feed saved in my podcast downloader, am enjoying all the music, and appreciate the effort. I don't listen to that much new stuff, and definitely not in many varied genres, so this is great.