Stuff on the web is often ‘free’. But it is not, really. Someone has spent a long time writing it, designing the code, or the artwork, or what-have-you. Online paying magazines need money to keep going.
So: if you enjoy something and find a site useful, donate some money.
Donate to Duotrope or Ralan if you use either site for finding places to submit to, or become a paying member of Querytracker if you use it a lot.
Join a writers’ association if you find their website helpful
Donate to a magazine if you support them.
Donate to a site that you use a lot for research
Five or ten dollars a year is fine. Just do it.