Deep-Sky Org
Science, Astronomy, Amateur, Deep Sky Observing - Deep-Sky Org. Features a reference of Messier objects, telescope information, images, and deep-sky links.
https://www.deep-sky.org/
Messier45.com
Science, Astronomy, Amateur, Deep Sky Observing - Messier45. News, observing guide, references, download, deep sky maplet, list generator, other tools, and help guide.
http://messier45.com/