Short answer - yes!
How you do it depends on exactly what you want to do. Also consider that Moodle is open source and has a highly pluggable architecture. This means that it can be relatively straightforward (and relatively inexpensive) to develop custom plugins to provide these links to external sources so it works exactly how you want it to.
It really all comes down to the details though - but it certainly can be done either with core code or readily achievable custom plugins