Here’s a great list of resource sites which any new webmaster would do well to link to. As Aaron suggests, it is about adding value to the search community and not about hoarding PageRank or link reciprocation.
Some of them are well-known like DMOZ, Yahoo Directory, Wikipedia, About.com and others such as Yahoo Mindset or Lii.org may not be as familiar to newer webmasters. It offers tips like how to search .gov and .edu sites with Yahoo which is particularly useful when needed to obtain quality information without putting up with the spam.