Online Wildflower Resources: I've found the following websites useful in my search for names and information about prairie wildflowers, especially after my visits to Grasslands National Park, where many native prairie plants grow.
Native Plant Society of Saskatchewan: Several online field checklists (as PDFs ) and guides. NPSS is on Facebook, too.
Saskatchewan Forage Council: The PDF “Field Guide: Identification of Common Range Plants of Southern Saskatchewan” has very clear line drawings of grasses, grass-like plants, forbs and shrubs. (Forbs = the broad-leaved herbaceous plants, i.e., not shrubs or grasses, that are an integral part of the prairie. aka potential wildflowers!) Also from the Forage Council, Field Guide: Identification of Common Riparian Plants of Saskatchewan. Good, clear line drawings of wetlands trees/shrubs, grasses, grass-like plants and forbs. (And yes, they have other guides, too.)
Perennial Gardening on the Prairies: This Saskatchewan site features photos of more than 400 native Saskatchewan plants, including foliage, leaves, stems, overall shape, etc. — very useful for identification, with a frames page for quicker viewing. (The pictures each include a handy ruler to show how tiny some prairie wildflowers really are.)
Saskatchewan Conservation Data Centre: The lists of images of Prairie creatures and plants is provided through a search page. (To confirm what's there, click the Common or Scientific name lists, or go right to the search.)
Colin`s Virtual Herbarium: Features pictures of flowering Prairie plants, with a focus on Saskatchewan, and includes pictures taken in the field and pressed specimens from the University of Regina.
What's in Bloom? (Royal Saskatchewan Museum, Regina, Saskatchewan)
Lichens: Bernard De Vries (Getting to know Saskatchewan Lichens) has written (with Irma De Vries) a number of online publications on lichens, including Prairie Lichens Series One (primarily soil lichens) and Prairie Lichens Series Three (primarily rock lichens). Series Two and Series Four feature Boreal lichens. There is also a De Vries field guide for lichens in Cypress Hills.
Native Plant Database: Recent search results for Saskatchewan wildflowers generated hits for 805 species, many with thumbnail images. Several ways to search; many different kinds of plants (trees, shrubs, ferns, vines, ground cover, etc.)
Manitoba Agriculture: Weeds: A useful site for identifying common Prairie weeds, especially that confusing Composite family (Sow thistles, Hawks' beard, etc.)
University of Manitoba: Weeds. Yes, weeds again — but a good site, with several images for each linked plant.
Ontario Wildflowers: As the home page says, most plants featured grow elsewhere.
Wildflowers and Scenery of the Canadian Rockies: Plants are indexed by common and scientific names, with several photos of each. Sections include the Rockies, Foothills, Prairies, Glacier/Waterton Area, and Alaska/Yukon/NWT, with a general search function.
Montana Plant Life: Saskatchewan borders Montana to the south, and so we have many plants in common — especially in the Grasslands. This site has a number of lists, including Native, Introduced, Edible, Medicinal and Poisonous Plants.
Montana Field Guide: The official state website for flowers — a lovely notion, and a good site.
Minnesota Wildflower Info: This site features an app, and includes trees, ferns, grasses and sedges.
Kansas Wildflowers and Grasses: Going further afield... Yes, I know Kansas is a little way from Saskatchewan, but we have many wildflowers in common and this is a lovely site. What could be better than flowers listed by logical colours (blue, purple, lavender, violet? white, green, greenish-white?), and displayed by thumbnails?
To be continued... Not that I'm still actively searching for more links, but as I find them I will add to this list — and if I've omitted your favourite Prairie/Northern Great Plains wildflower identification site, please let me know! (No commercial sites, i.e., plant sellers, please.)