My number one site (shamelessly excluding this blog, of course) is Ancestry.ca, the Canadian 'edition' of Ancestry.com. There are 'editions' or versions of the Ancestry site for several countries, such as the United Kingdom, Germany, Australia. The Ancestry site provides a number of free tools and information but it is a paid subscription based site for database access. The databases are fully searchable and provide either electronic image of the original document (that can be saved to your computer) or indexes of records. With a World Deluxe subscription, the databases associated with all countries can be accessed which comes in handy when I am helping friends get started with their research. In addition, the site can be used to post and share your research results through a family tree that allows you to connect with others who may be researching the same family lines - like cousins you didn't know about!
Number two has to be Google, and I include in this Google maps, books, images, etc. Not only do I find great benefit from general searching for information but the site offers search techniques, many of which I have yet to discover, such as timeline searching to help set better historic context for the events and happenings in the world in which my ancestors lived. Google Books provides access to the full or partial text of many public domain books, some of which can be downloaded in PDF format for later reference.
As my paternal side is Scottish, my number three site is ScotlandsPeople.gov.uk. ScotlandsPeople is the official site for the government records of Scotland such as birth, marriage, and death registrations, census records, parish records and, wills and testaments. The site offers pay-as-you-go searching of the records - essentially you purchase credits and use the credits to view search results and document images. Although I find some of the database search criteria to be a bit limited, I have been successful at finding hundreds of family records and at a price cheaper than a trip to Scotland to search in person. The site is seen as a model by the heads of many jurisdictional archives as the best way to provide access to historic documentation and records.
From a Canadian perspective, the sites of Our Roots (ourroots,ca) and the Canadian Genealogy Centre of the Library and Archives Canada (collectionscanada.gc.ca/genealogy) has to be listed at number four. Our Roots provides fully searchable access to thousands of Canadian local history books through a national network of libraries, archives, universities, colleges, businesses and associations. The Canadian Genealogy Centre provides searchable access to the record collections of the Canada's national archives, Library and Archives Canada, although the number of viewable documents remains limited.
Rounding out my top five is GenealogyWise (genealogywise.com) which is a 'Facebook'-type social networking site for genealogists. Registration is free and once registered, you can join special interest groups such as those set up for different software programs or geographical locations or surname groups. The site provides the ability to connect with other genealogists to share suggestions, seek help, and make friends.
Finally, although not purely a site, I recommend listening to genealogy podcasts that can be listened to through your computer from the podcast website or downloaded if you have access to a digital media player like an iPod (from which podcast gets its name). My favourite is The Genealogy Guys produced each week by George G. Morgan and Drew Smith (genealogyguys.com). George and Drew have been regularly producing their podcasts for over four years and this past week they even mentioned this blog - quite the honour for me! Another excellent podcast to recommend is Genealogy Gems (genealogygems.tv) produced by Lisa Louise Cooke. Listen, learn, and enjoy!