[Belar]

Pretty much always you can "give them a $20", every medium+ sized project has some kind of support program going or accepts donations.

However, if they don't or someone doesn't have a $20 to throw at open source, there are a lot of ways to help. Just to mention a few (assuming you are at least an active user):

- help less experienced users (answer community questions, reported issues etc.),

- improve documentation (documentation is never finished),

- share your knowledge about a tool (write an article, tutorial),

- take part in tests and report bugs,

- apply your skills (design, writing, community management etc.) to aid project's needs,

- create (and maintain) a useful "resource" (e.g. list of example projects, plugin reviews).

There are many ways that often go "unnoticed" or rather... no one may officially pat you on the back for it, but it helps.