In the industry there are a few favourite resources we return to again and again. One of these is the Heritage Perennials site www.perennials.com. Here you can find top 10 perennials of the year, perennials 101, design tips, gardener resources, videos and more.
Here's a peak at their home page:
A few minutes now meandering around the site will show you it's value. Whether you are looking for design ideas or want information about a particular perennial, this site is an excellent resource.
I'm sure you have a favourite go-to site for gardening. Feel free to share in the comments. I'm always on the lookout for more resources. Cheers!