In my Best Practices For Web Form Design talk at IA Summit 2007 I walked thorugh the importance of Web forms and a series of design best practices culled from live to site analytics, usability testing, eye-tracking studies, and best practice surveys.
My Slides from the talk: Best Practices For Web Form Design (3.9 MB PDF)
Some of the topics I discuss and provide patterns for are: label alignment, required form filed, input field sizes, content grouping, primary & secondary actions, help text & tips, dyanmic help systems, inline validation, error messages, progress indicators, success messaging, progressive disclosure, gradual engagement, tabbing, flexible data inputs, smart defaults, paths to completion, selection dependent inputs, and more...