A web search (google) by common or Latin name of a tree species may lead you to commercial nurseries or sales sites, but among the listings, you should be able to find the following:
USDA Plants Database:
Select the proper category in the “Name Search” drop-down list, then type in the name of the species for which you are seeking information.
Selecting the Profile (pdf) will provide you with a fact sheet.
UCONN Horticulture web site:
This site is searchable alphabetically by Latin or Common Name. Scroll through information that appears on the left side of each page and click on thumbnails to see larger pictures.
Silvics of North America:
Searchable by Latin or Common names, Volume 1 is for Conifers and Volume 2 is for Hardwoods. Covers all commercial species in North America, not just CT.
Virginia Tech Dendrology
A very helpful tree identification resource with fact sheets and photos.
There are many other good web resources as well, but these sites are comprehensive and reasonably user-friendly.