Air fare websites

www.skyscanner.net is very good for finding who flies where & when - especially if you click ‘Monthly View’.

I now use Skyscanner also. Years ago I used Kayak, then abandoned it for some reason, and started using Hipmunk and Skyscanner. However, when searching for flights for next spring recently, I found that Hipmunk was often inaccurate. So now I'm just using Skyscanner.

Google Flights is handy too.
Whichever search engine you use, the general wisdom here is to book directly with the airline once you've identified your preferred flight - saves a lot of aggravation if you're dealing with the airline directly versus working thru a 3rd party booking site to resolve any problems that may arise.

I like Momondo for comparing fares across different dates and finding cheapest vs fastest routes. I also like the Google flights map for identifying all the airports and looking at fares across a geographic area. I use both for research and once I've identified my preferred flights then I book at the airline's site.

googleflights