How is it possible to access microbiome data like that found here? I'd like to perform analyses on similar type of data, but cannot find OTU data like that at the Human Biome Project. Thanks for any leads.
This .csv files (comma-separated value) can be imported into Galaxy (usegalaxy.org)
I recommend that you take a look at that web app, it has many build in applications for analysis.
Also this site has a lot of quick video tutorials.
The data that you are pointing to are files in .csv (comma-separated value) format. They can be opened, after downloading, by any standard spreadsheet programme, including Excel, as well as programmatically (e.g. in Python using the csv module)
Apologies if you understood this and were asking for something more.