If I need to find an article by name or author, but I'm not doing a systematic search: Google Scholar
If I'm looking for something by keywords: JStor
Proquest allows more in depth searches, I think, like looking for dissertations/theses, etc.
EBSCO and ERIC are okay but I can't stand the interface.
I used a bunch more one time for a meta-analysis I worked on, and I left feeling that databases like Proquest and EBSCO are great for finding every article possible related to something. But my go to is JSTOR because it tends to pick up more relevant stuff for me.
YMMV.