oliverthiele/ot-formprefill
TYPO3 extension that automatically fills in form fields for logged-in frontend users using values from fe_users. Includes optional FlexForm-based field mapping and works with existing forms.
datamints Forms GET Prefill
Prefills form fields by URL GET-parameters. Works with EXT:powermail & EXT:forms
Search form: Prefilled search phrase
Shows search results for the search phrase the visitor looks for (e.g. via google or yahoo)