Robber Flies of the World by Chris Cohen – A framework that includes all modern taxonomy and worldwide catalog. I encourage you to check out the catalog, where you can develop a list for any region in the world based on museum records.
Robber Flies by Fritz Geller-Grimm, Torsten Dikow, & Robert Lavigne – There is a lot of great information on robber flies, but the reason I visit this site often is because of the fantastic anatomy terminology pages, which are a must when navigating old keys.
Asilidae on BugGuide – Essential.
Robber Flies of Florida on iNaturalist – Project focused on the distribution and phenology of robber flies in Florida.
SCAN Collections – A database where you can search museum collections easily. Essential data.
Robber Flies by Herschel Raney – One of the first websites on North American robber flies. Focused on Arkansas, but he includes information for the entire U.S. The state lists are very helpful as is the key to eastern U.S. genera.
Robber Flies of Georgia by Giff Beaton – Excellent resource for the southeast, though it seems to be down right now.
Robber Flies of Wisconsin by Mike Reese – Beautifully arranged website of all Wisconsin species
Robber Flies of Texas by Greg Lasley
Laphriini by Stephen Bullington – A website devoted to Laphria of the U.S.
Robber Flies by Michael Thomas – A whole page of frameable Asilid photos, including many southeastern species.