It's extremely helpful for aspiring designers to be able to hear from someone who is a respected and accomplished designer about the process of designing games. In this respect, there is no one better than Reiner Knizia. The following is a link to a podcast that was done by Dirk and Aldie (the co-creators of BoardGameGeek). In spite of the fact that Dirk is trying too hard to be funny in this podcast, Dr. Knizia offers a lot of interesting tid bits about designing games. Here's the link:
On the other side of the issue, it's important for aspiring designers to know how publishers select games and how the publishing business works. In this respect, there's no one better to hear from than Jay Tummelson - owner of Rio Grande Games. The following is an hour long interview with Jay that was posted by Boardgame Babylon and it's just chock-full of relevant content. Here's the link:
Update: It appears that these links are no longer active.