Airline schedules
 

I can't seem to find this anywhere, even when googling. But what is the website that lets you see all the flights between different city pairs. I've started jumpseating, and would be nice to look up other airlines timetables online in case i get stuck.

This website under under airline profiles to the left of the page.

If you commute or travel often and have the spare change- the OAG travel guide is the way to go. It has every flight worldwide and is updated regularly via the various reservations systems and ticket warehouses.

Get a subscription ($200/year or $16.95/month for online access) and deduct the cost as a work related expense.