Hornsby Council (Sydney) has just launched an easy-to-use online herbarium that can be accessed here.
The online herbarium catalogues hundreds of native plants (& some weeds) found in the Hornsby Shire but also found commonly in other Sydney Vegetation, and is a database allowing users to search through it for plant identification purposes. The Online Herbarium features easy searches using thumbnail images, large downloadable scans of live pressed plant material and a great search tools that allow you to search by: where the plant was collected (eg a specific reserve); what type of plant it is (eg a shrub); specific descriptions (eg flower colour); and advanced search tools. You can also search using the botanical search through classifications, plant families, genus type or species type.
The Botanic Gardens Trust (Sydney) has setup a great Cumberland Plain Woodland website, including an image library and plant species information.