Trello or Asana is pretty easy to use

https://asana.com/guide/explore/videos/crm

Plus you can use those for your projects/tickets/personal todos too.

I hate having <Dr Evil>one million</Dr Evil> webapps to do <Dr Evil>one million</Dr Evil> things. Even if they aren't best in class for _everything_ there is something to be said for _good enough_ in a single location