Yep, we use trello, it is a Kanban board style of project management (https://en.wikipedia.org/wiki/Kanban_board).
We are a smaller team, and I found a lot of the all-in-one CRM platforms were either more than we needed or just too archaic of a UI. Trello was simple, clean, and easy for us to jump into.
One of Trello’s secret weapons is the ability to link up with other online service that you may already use. You can connect it directly with services like dropbox and slack, letting you fill in the gaps of what it can’t do with other online services.
We actually have it connected to an online automation service called Integromat, which allows for even more under-the-hood connections, and lets an event from one service trigger an event in another services. eg. New project in trello also creates a folder on dropbox with the same name, and a line item in our billing software, etc.