Things I used in the past are:

• Finnish for Foreigners

• Finnish: An Essential Grammar

• Finnish for busy people

• Tampereen Yliopisto’s Finnish grammar guide

• ILoveLanguages — Finnish Lessons

• Jyväskylän yliopisto — Finnish Grammar Guide

• Glosbe.com

• Finnish courses on Memrise

• Finnish learning on WordDrive

And if you are ready to use a textbook that is actually written in Finnish instead of English, Suomen Mestari is an extremely good resource and it is available in pdf form online on sites like MediaFire, but I’m not gonna link them just because by nature file-sharing sites are not exactly the most trustworthy, so I’d rather just let you (or whoever) do that on their own than send you there directly. But it is out there if you want it.