A post on the "Simple Dollar" Blog outlined 10 ways to create value from your web surfing. Professionals can use many of these ideas to build their reputation online and obtain more links and traffic to their websites. I think the point that Trent makes about sharing only useful and relevant comments is important. Not only will you be wasting the blog owner's time, and other visitors' time reading a useless comment, but it dilutes your online reputation, which is more important than you might initially think. I also suggest that you use your real name, whenever possible, when interacting online, since it shows integrity. My own additional tip is to have an easy way to gather and share items you find (whether through blogging or a bookmarking service, etc), since you do need to be able to efficiently gather and share your finds, or you will not bother to do it.
Source: The Simple Dollar » How to Get Personal and Professional Value from Idle Web Surfing