Algaebase
http://www.algaebase.org

A huge database of marine algae that you can search by distribution, genus, species, literature or image. They have hundreds of images. Quite a technical site.

Beyond the reef
http://www.austmus.gov.au/exhibitions/beyond/

An exhibition at the Australian Museum looking at plankton with pages devoted to the different groups of plankton.

Introduction to the Phaeophyta Kelps and brown "algae"
http://www.ucmp.berkeley.edu/chromista/phaeophyta.html

The largest of the chromists are the Phaeophyta, the brown algae -- the largest brown algae may reach over 30 meters in length.

Part of the The Museum of Paleontology, University of California, Berkeley web site.

KelpWatch
http://www.kelpwatch.tas.gov.au/

''KelpWatch'' is a community-based research and monitoring project aimed at assessing the current and past distribution and health of Giant Kelp forests in Tasmania.

The site has a great deal of information on all aspects of kelps.

SeaCare
http://www.seacare.org.au/

SeaCare is a community based group formed to facilitate projects aimed at benefiting the marine environment in Tasmania. So far activities have focussed on the restoration of Giant String Kelp (Macrocystis pyrifera).

There is quite a lot of information about kelps as well as about the restoration project on the site.