MixPanel can do this and they have a free plan.

I custom-built my own cohort reports but as number of users grow in my own app, I'm planning to replace it with MixPanel. You don't really want to put stress on your own database servers which are meant for production, not for analysis.

You should not be doing analysis (OLAP) on your main transactional database (OLTP). Moving from transaction-processing system (TPS) to analysis is done through a process call ETL (Extract, Transform, Load.) You will want to transform your data into facts and dimensions -- this is going from a relational model to a multidemensional model (using a star schema.)

but that would be another system to maintain. I'm happy to outsource this to MixPanel or some other company. My needs are pretty generic. I appreciate your response though.

Yes, I 100% believe in focusing on your core competencies. If the OLAP is self-hosted or external, the key takeaway is to not do analysis against production (once your data set is larger than RAM ;) before that, who cares?)

Cohort.ly does a great job. They are in private beta so you can request access. It has been really beneficial to us.

http://cohort.ly/

I really dislike this trend of only having videos to share info about a product or service.

Not even a blurb on there.

have a look at https://github.com/Doist/bitmapist - some more info here http://amix.dk/blog/post/19718