I've seen a huge uptick in spam email the last few days, and although I have no indication that I've been hacked, I feel as though I should probably fear for th

I've seen a huge uptick in spam email the last few days, and although I have no indication that I've been hacked, I feel as though I should probably fear for the worst and aggressively change all my passwords from their current kindergarten security levels. Is there a widely accessible, secure, multi platform, free/libre password manager that is recommendable as easy to use? I reuse passwords because its easy to remember, and I'm hoping there is something out there that is light years better than those I found the last time I tried (2007).