oDesk knows how painful can be to write up once again a job post description, even more if it’s for a small job. That’s why they give you the option to reuse some of your previous job posts.
Heroku allows you to deploy just by using your Dropbox account. I don’t think this way of deploying is the ‘by default’ by pro developers, but I do really think is a great idea to get a way to reach all the Dropbox’s audience and give them n easy&faster of deploying – even if they have not heard about ‘deploying’ before.
Buffer provides a WordPress plugin (digg digg) to make it super-easy the way of sharing content of your blog. Even if it’s not their core business the development of WP plugins, they know their vast majority of their users might be using WP as platform to blog, so why not to make the path easier
Once you add the KimonoLabs add-on to your browser, it shows a figure with the number of current APIs created by other users in the page you are currently browsing.
Booking does a great trick using notifications. Even if you are not a member of their platform, they mimic the notifications a user might receive if he’s logged in his account. First impulse when seeing that you have a notification? Click on it. They take advantage of this fake notification, to encourage you to signup for ‘exclusive member deals’.