It is possible to create links to other webs on the same Instiki installation, either by web name or address (both are defined on the Edit Web page):
An interweb link by address: [[jrblevin:HomePage]] yields HomePage.
An interweb link by name: [[Jason Blevins's notebook:HomePage|my notebook]] yields my notebook.
Note that it is still possible to use alternate link text in the usual way, as in the second example.