[drupal-support] re-inventing the wheel

I've seen a number of Drupal sites where one can click on a link to donate (e.g. political campaign web sites). The user is then presented a form to fill in some required information and then given a button to go to Paypal to finish the transaction and donation with a credit card.

Building the page to go to Paypal is the easy part. But what techniques are people using to capture data and then forward the user to the next page? I'd rather not re-invent the wheel, and I'd also like to avoid having to implement a module to do this. Surely there is an easier way.

Any suggestions or sample code I could look at out there?

Thanks, -- Chris Johnson