HuGENavigator is "an integrated, searchable knowledge base of genetic associations and human genome epidemiology" - HuGENet is a CDC based project.
Phenopedia - search this for genes associated with a disease
Genopedia - search this for diseases associated with a gene
Literature - search the literature (no, you don't say!), since 2001, with links to PubMed records. This has to be some sort of filtered search (searching for macular degeneration finds 171 records, where a straight search of PubMed for the same timespan finds 6500) - I can see that it searches MeSH and text, and that you can use "query detail" to deselect MeSH terms or tell it not to search free text, but haven't seen any more details as yet.
Investigator - search for a gene or disease to look for people working in an area (shows number of papers with that author as first or last author)
Gene evidence - are there genes that might be associated with a disease - not sure how this differs from Genopedia above, unless Gene evidence is looking for probable associations, not definite investigations?
Trend/Pattern shows you trends in literature, diseases or genes studied, and gives you a graph - this does show how this area has grown, even if it doesn't show you much detail.
Lastly, there is Risk, which enables you to evaluate the predictive ability of genetic markers. You would need more knowledge than I to be able to say more about this!
Some time ago I did a handout on clinical genetics resources, for a visit I made to staff at the Clinical Genetics Centre at the Leicester Royal Infirmary. I have revised it since, for genetics students, and have revised it again today to include HuGENavigator. The handout is at http://www2.le.ac.uk/Members/khn5/other-stuff