WolframAlpha Widgets are mini applications built on Wolfram Alpha queries. You can share them in several ways - Facebook and Twitter for example or embed them in a blog or website. Either use a widget from the growing gallery (note the categories on the right) - see Mathematics here or create your own.
See Wolfram Alpha’s own blog entry.
It is possible to embed a widget as shown here. They can also be shared on sites such as Facebook and Twitter.
Craig Barton is busy building a great widget collection for students to use to check their work.