Oh gosh, I have so many of these I could probably share.
The Gymnosperm Database (http://www.conifers.org
This website is a great storehouse of information about gymnosperms. It features some beautiful botanical illustrations, distribution maps, ethnobotanical lore, and is properly cited and referenced.
Botany Photo of the Day (http://www.botanicalgarden.ubc.ca/potd/
The University of British Columbia regularly publishes gorgeous photos and an accompanying article showcasing the wonderful biodiversity of our botanical brethren.
Illinois Wildflowers (http://www.illinoiswildflowers.info
Perhaps the most beautiful plant reference I have come across. Though the distribution maps are specific to Illinois this resource is useful for anyone who lives in ecoregion of the United States that will share species with the state.