I have a SharePoint list that I wanted to populate with data from an InfoPath
form. Originally, I used the previously suggested method of CAML and VB or C#
code (detailed at
http://enterprise-solutions.swits.net/infopath2007/article.php?t=programmaticall
y-add-item-sharepoint-calendar-infopath&c=infopath2007
and
http://www.infopathdev.com/howto/tutorials/default.aspx?i=7bc880f391b84ea9b3b45c
6fbecc07c6).
This method, however, proved to be unnecessarily cumbersome. I've found what
I consider to be a superior method: SharePoint workflows. You can create and
update SharePoint list items using this method:

1.) Create a SharePoint form library.
2.) Create an InfoPath form with whatever fields you want to send to a
SharePoint list.
3.) Configure a button to submit the form to the previously created form
library.
4.) Publish the form to the library, making sure to map to columns whatever
fields you want to send to the list.
5.) Open the library in SharePoint Designer and create a new workflow.
6.) Set the workflow to run on new items.
7.) Configure the first step in the workflow to create a list item.
8.) Map the fields from the current item, your InfoPath form, to the
appropriate SharePoint list.

Now all you need to do is fill out the form and click the submit button. The
fields you mapped in the workflow will automatically populate the list. I
apologize if this has already been pointed out.