Ecosystems + Biodiversity
http://www.fi.edu/tfi/units/life/habitat/habitat.html

IB ESS wikispaces, there are some useful things in there, just have to look for them!
http://ibess.wikispaces.com/Home

Some background/side knowledge of Topic 3
http://www.overpopulation.org/solutions.html

Great blog, include some study notes for ESS for further reading; but the study notes is only up to Topic 3.
http://yesitsyomoma.wordpress.com/category/environmental-systems/

Mr Bruford's sites, but only up to Topic 3 as well.
http://web.me.com/richard_bruford/My_Site/ESS.html

Good sites for ESS studying but there are some missing assessment. There are also some review question on there as well.
http://sciencebitz.com/

Information on Topic 3.8
http://dieoff.org/page112.htm

Very average website, got limited useful material in there
http://www.tokresource.org/tok_classes/enviro/syllabus_content/index.htm

Great website, have lots of note but you need to download most of them. Lots of online resources as well. But this website is missing bits and pieces of the syllabubs...
http://www.mrkremerscience.org/2010_Site/IB1_ESS.html

Havn't listen to it yet, but by the look of it- its related to ESS in some way.
http://ax.itunes.apple.com/podcast/earth-environmental-systems/id254904935

Wikipeida is always useful
http://www.wikipedia.org/