OP_RETURN

Writer
Write text to Memo.SV or B://
B-Kitten
Upload big files with the BCAT protocol

BitBtn

A web button that generates Bitcoin transactions and sends them to your wallet
Btn Page
A landing page, prompting for a transaction. Highly customizable.

External

BitcoinSofia
Practical Bitcoin Consulting
The PipeCash Project
Automation with a pinch of Bitcoin