I track all of my figures in Trello. I use it for a number of things, and for the project management and development minded among you, you're already familiar with Kanban boards I'd imagine - and that's what this does, so you can build everything in the collection by pending, building, painting and finished.
You can make it as detailed as you want and I like to group by units or teams and track progress. So it's a lovely way for me to check what figures in a team I have, which are completed and what's still to-do. It's been quite helpful in the last eight months on tracking progress across multiple projects.
Then I keep a number of different labels by game or manufacturer, and you can filter on those to see where everything else is.
The below gives an indicator of how woefully behind I am on painting up my Guild Ball teams ...
... but when's the small matter of 500+ unpainted figures ever slowed a painter down, right? Right?
Anyway, it's great to watch the pile reduce and have listed outputs as a little motivational kick, especially when I've lost track of the figures I own and incentivising myself with "treats" of completing a team set with new releases, or being out at a show and ensuring I don't pick up something already in the collection.