Nasa Open Datasets
open.nasa.gov
open.nasa.gov
[1] http://datacasting.jpl.nasa.gov/
[2] http://datacasting.jpl.nasa.gov/feed_directory/
Disclosure: I work for the company that helps run data.nasa.gov
The search capability (e.g., https://news.ycombinator.com/item?id=10264811) returns so many results for typical naive queries ("temperature" returns 8300), that it's impossible to sift through them. They seem to be un-curated, so a niche product with marginal calibration gets equal play to flagship products with thousands of users.
People like me who use lots of this data every day have sat in panels and workshops and mused whether a searchable top-level index would be useful, because this is not how scientists work. They ask their friends which sources are best for their use, e.g., which have the right coverage and sampling in space, time, and wavelength. And they settle into something, and maybe make a big shift to a new product when it comes online.
But: something like this index could be helpful, to citizens, decision-makers (e.g., tree canopy depth maps for fighting forest fires), and to out-of-discipline scientists ("what if I brought in NASA sea surface temperature to my analysis of beach restaurant revenue fluctuations?").
For CO2, here's an example (https://co2.jpl.nasa.gov) which gives 5 simple use cases and sketches why you'd choose one over the other.
I can't see more than two items on this page: https://data.nasa.gov/data?&search=&type=datasets I'm just after a big list of datasets so I can skim through and find ones I'm intrigued by. Here's a screenshot: http://i.imgur.com/TtP630G.jpg (latest Chrome, mac)
The featured dataset links to a 404 page: https://open.nasa.gov/nasadatanauts/
Again, great to see the data out.
Edit - scratch the listing problem, it seems to be one of my extensions, either readability or pushbullet, breaking the site.
In Michigan mappers, citizen activists and journalists are drawn to it in equal numbers with developers. Giving different views that allow them to get what they're looking for is very powerful.
SkyWatch is doing something similar. If you're into this sort of thing, check them out.