End user sign in and/or registration template example I'd like to create a template that lets visitors either a) register a new account or b) sign in to an existing account.

There's a sample public registration form here: http://buildwithcraft.com/docs/templating/user-registration-form.

However, I can't find any examples of how to enable a visitor with an existing account to sign into it.

Sorry if I'm missing an obvious link somewhere.

How do you do this? Thanks!
Here is an example of how to do a login form for users with existing accounts: http://buildwithcraft.com/docs/templating/login-form

You can see more form examples in the left hand menu of that page.