This post explains how to use the Salesforce.com Web-to-Lead form when you are using NFP Success Pack.
Surely you have seen the recommendations from Salesforce Foundation that you should not activate Person Accounts if you are using NFP Success Pack (NPSP) for your Accounts and Contacts.
By default all Contacts stored in Salesforce.com need to be associated to an Account to be viewable by other users. This model is not applicable to many Contacts (supporters) in non-profit organisations. Salesforce NPSP has a solution for this model.
Assuming that an individual that fills your web-to-lead form is not from a company which means that the company field will be left blank. Once the form is submitted this is how the lead record would look:
To read more about Salesforce Foundation and the Apps that your organisation can benefit from click here.