Doc Searls mentions that a google search for "podcasts" in September 2004 yielded only 24 results. I just repeated that search and got 270,000,000 results. An interesting note is that Yahoo Podcasts, the fourth highest result is announcing that it will close as of October 31st.
Government podcasts continue to grow in number, but often remain in oblivion. GovWatch recommends that government do a better job of marketing the content they produce, including the use of channels such as Wikipedia, Technorati, Digg, DMOZ, etc. Based on the recent emails that I have received from the Government Content Managers Forum, many are doing exactly that. There was a lot of discussion about the effective use of Wikipedia which has became the #8 site on the internet. For example, the US Forest Service has a very useful Wikipedia page with graphics, links, and useful info. In fact, I found some information links there that I had never seen before.
Many government podcasts are listed on freegovinfo.info, such as CoreCast from USGS.
The US Plants database is an amazing resource. Perhaps even more, is the Global Biodiversity Information Facility Data Portal. This resource has geo-based information for species and other groups of plants, animals, fungi and micro-organisms, including species occurrence records, as well as classifications and scientific and common names from around the globe.