1.Developer combine a build-in Bitcoin client with his software.
One interesting use of an integrated Bitcoin client in a software would be to facilitate the donations for open source projects.
You go to menu Help > Donate or something, and instead of a Paypal button or link to a donate webpage, you have a send Bitcoins buttons.
On first use, the software would generate a new secret address that you can send bitcoins to before making the actual donation, and then in the special donate dialog you can choose to send all or part of what you credited to this address.
The actual bitcoin clients could experiment with this.