Navigating through hypermedia the user faces problems of locating oneself with respect to space and time. That is why there is a need to develop tools that can help the user locate himself to see where he has been browsing through the net during a particular navigation session through hypermedia. It is needed to offer the user a map of the visited sites, allowing him to have an explicit representation of virtual space. We first introduce the concepts related to hypermedia navigation; we then present an overview of different computer aided navigation tools and techniques. We conclude by presenting a comparative table of these tools based on some pertinent criteria. (Contains 1 chart and 1 diagram.)