During the development of the geoRSS widget for ExploreOurPla.net I used this list for testing:

newsrss.bbc.co.uk//rss/newsonline_world_ …
rss.news.yahoo.com/rss/climatechange …
rss.news.yahoo.com/rss/earthquakes …
rss.news.yahoo.com/rss/hurricanes …
rss.news.yahoo.com/rss/nasashuttle …
rss.news.yahoo.com/rss/science …
science.nasa.gov/podcast.xml …
today.reuters.com/rss/worldNews …
tools.wikimedia.de/~dapete/wikinews-rss/ …
volcanolive.blogspot.com/atom.xml …
www.cbsnews.com/feeds/rss/scitech.rss …
www.climateark.org/rss/climate.xml …
www.csmonitor.com/rss/top.rss …
www.ecoearth.info/rss/ecoearth.xml …
www.enn.com/news/rss/today.rss …
www.envirolink.org/environews.rss …
www.exploreourpla.net/?feed=rss2 …
www.fas.harvard.edu/~cscie1/podcast/ …
www.ftd.de/static/container/rss/ftd-rss2 …
www.nasa.gov/rss/NASAcast_video.rss …
www.nytimes.com/services/xml/rss/nyt/Sci …
www.pbs.org/wgbh/nova/rss/nova-vodcast-p …
www.pbs.org/wgbh/nova/sciencenow/rss/nsn …
www.presseportal.de/rss/umwelt.rss …
www.scidev.net/newsfeed/rss/newsfeed-1.x …
www.scienceticker.info/rss/RSS_File.xml …
www.spiegel.de/schlagzeilen/rss/0,5291,2 …
www.tcsdaily.com/rss/main.xml …
www.terradaily.com/terradaily.xml …
www.unicef.org/rss/unicef_television_vod …
rss.dw-world.de/xml/podcast_corresponden …
news.search.yahoo.com/news/rss?p=Climate …
news.google.de/news?num=20&q=climate+cha …
news.google.de/news?num=20&q=Global+Warm …
news.google.de/news?num=20&q=Greenhouse+ …
www.planettvshow.com/mov …
www.discovery.com/radio/xml/sciencechann …
feeds.feedburner.com/SpacecomUniversalSp …
earthquake.usgs.gov/eqcenter/recenteqsww …
earthobservatory.nasa.gov/eo.rss …
esamultimedia.esa.int/multimedia/esc/esa …
yosemite.epa.gov/opa/admpress.nsf/RSSRec …
www.eea.eu.int/XML/highlights.rdf …
rss.slashdot.org/Slashdot/slashdot …
www.cep.unep.org/news/RSS …
www.who.int/feeds/entity/csr/don/en/rss. …
news.ft.com/siteservices/rss …
www.alertnet.org/thenews/rss/index.xml …

It is a mixture of international ressources. Registered users can edit their feed list in the extended profile very easy. Unregistered users have a predefined list, but can browse any feed, when it is properly included in URL.

There are still some issues with Microsoft Internet Explorer, use Firefox instead to avoid them.

Just in case you are still wondering, see geoRSS in action. Next version will have different colored icons for any feed.