Great post and I love anything that raises awareness about the free resources provided by archive.org. Some of the information is inaccurate though: Wayback Machine crawls do include MP3s or any other file types, provided they are served up by normal HTTP or HTTPS download links and not hidden behind flash players or MediaFire-type download sites. As with any Wayback Machine content it can be hit and miss as to whether any particular link gets archived, although they have been improving over time. I highly recommend just using the archive.org file area to host the MP3s in the first place - free bandwidth!

Submitting your site to be archived is another very useful feature, however it will only archive the specific URL you give it and does not actually trigger a crawl of the entire site. The six months blurb you quote was in reference to the previous situation where URLs archived by Wayback would not go live until months later when the indexing and such had been completed. This is no longer the case and archived URLs are now available within seconds.

If you have a full site that needs crawling you can bring it to the attention of the Archive Team (http://archiveteam.org/) and we have tools that can make that happen and import the results into Wayback.