Cool! It's been super useful personally and hard to describe without sounding scammy because people don't believe there's free money just sitting out there.

Need to put some more work into it, but there's so many sites that could be added and the bonuses really tally up if you collect from all of them (I have a running list and right now it's around $20/day in bonuses if you collect from every site on the list).

I think someone maintains a spreadsheet of these that I came across on reddit. I'll come back and post it here later if I can dig it up.

So how do you withdraw the funds? Or do they sit in the online casino's site for you to put a bet on or something?

It sits in the online casino's site. Some sites require you to play through the bonus once, while others allow you to withdraw directly once you reach a certain balance. For the ones that require you to play through, I just play the bonus through low-volatility slots.