[@http://www.boost.org this is [*boost's] website....]

will generate:

this is boost's website....

URL links where the link text is the link itself is common. Example:

see http://spirit.sourceforge.net/

so, when the text is absent in a link markup, the URL is assumed. Example:

see [@http://spirit.sourceforge.net/]

will generate:

see http://spirit.sourceforge.net/

Boostbook also support a custom url schema for linking to files within the boost distribution:

[@boost:/libs/spirit/index.html the Boost.Spirit documentation]

will generate: the Boost.Spirit documentation

Note that this is only available when using BoostBook, and only for links - it can't be used for images.