If they have to be more memorable than secure I use DinoPass and make a few changes like uppercase or adding a !@#$%^& between words
I think there is a built in feature in firefox which always gives me strong passwords option whenever I visit a new website. And it remembers complex login details such as usernames and passwords so I don't have to remember them or save them manually. So if you have firefox then you don't need any other such service.