Hi Meghan,
Meghan, I did look at the webform site you provided in your first post, and I have to agree with everything Mark has already said, thanks for the help Mark. The URL post method used by formsite website you are talking about is essential what Method is using in our own webforms. This is how Method retreives the data that has been entered in the webform after the user has clicked the "submit". Unfortunately there likely wouldn't be any easy ways to integrate the Formsite webforms with Method's, it looks like you would have to use one or the other.
I do see the advantage of creating a webform using Formsite (based on your last post), I can see you can get quite advanced with their webforms. Depending on how important it is for your site to incorporate a more advanced webform like Formsite can offer, there could be a way to take the submitted information and send this to your Method database. However, I believe you would need to use the MethodAPI to do something like this, but that would be well beyond the scope of these forums. If this is something you are considering, you might considering taking a look at this link. Here you can generate a list of all Method Solution Providers that might be able to help you figure out a solution for this, I would make sure to check off the option for "I'm looking for someone who has experience with the Method API". There are several Method Solution Providers that have experiencing working with our API, you might notice Mark Crews from this thread, actually shows up on this list!
As Mark also suggested, you could likely work out what you are trying to do through a Method WebPortal (located Customize->Portals). The Method webportals offer HTTPS security, and give your users the ability to login to their own accounts so they can only access their information, and whatever information you have setup for them to access. Here is a link which explains how to setup a portal from within your Method Account. It could be a thought to create screens in this portal that act as a webform, but no webform would be necessary.
I hope this helps,
-Ben