a plugin to let customers change their data?

I am looking for a simple plugin that lets users create a little account and put in some info (fill out some forms) and then gives them the ability to log in later and change that info.

Ultimately, I’ll be using this to have customers purchase products (the actual purchasing will be handed off to Paypal) but the e-commerce plugins I have seen are either far far far too complicated and in depth (one installed a completely seperate instance of wordpress) or they don’t have the login capacity so users can keep track of their data (eg, cancel subscriptions or update their address.)

Any suggestions? Thanks!