Custom User Profile and Registration/Subscription fields

Hi all,
I've searched a lot on support forums but I was not able to find a clear answer to a simple question.

Is there a way (without using buddypress)
to customize the signup/subscribe form adding some extra fields and templating it a little bit?
and is it possibile to let users manage theese custom fields even on their edit profile page?

would be great, for example, if one could integrate a plugin like Theme my login ( or others like that to work with your awesome Membership

buddypress is really nice, but for a lot of projects is far too complex especially when you have to develop a site that is already online with a lot of registered users