When you don’t already know the address of a particular page of information you need a search engine.  A good one when you’re starting off is Ask Jeeves! http://uk.ask.com – this site allows you to type in questions such as ‘Where can I find a map of Little Snoring?’ or ‘Canada tourism’ and then provides links to likely web sites.  A very comprehensive one is www.google.com  But don’t get fixated on a single search engine - they all have strengths and weaknesses, and the same search on a different search engine may bring better results

The main starting point for genealogy is Rootsweb www.rootsweb.com  Rootsweb started life as a co-operative but rapidly grew to become very expensive to run.  In July 2000 they went into partnership with a commercial genealogy company Ancestry.com but have said that their impartiality and independence will not be compromised – time will tell.
Rootsweb provides everything you need to get started on line: a comprehensive guide to tracing your family history, links to all other major genealogy sites, pointers to all the mail-lists (where you can sign up – free – for discussion on specific aspects of genealogy), a vast searchable surname database and bulletin boards for queries and discussions relating to those names. 
The one criticism some people level at Rootweb is that it is American-based and has a lot of American material.  That may be helpful, as most of us have emigrant ancestors somewhere in the tree (as we found through DNA testing - see below), but don’t overlook the wealth of material which relates to the UK – many Americans need to access UK sources when they follow their roots back far enough. 

However the major site for UK research is http://www.genuki.org.uk  (Note the correct address – a commercial organisation has registered the addresses genuki.com and genuki.co.uk to try to exploit Genuki’s reputation.)  The ‘real’ Genuki has a ‘top-down’ structure whereby you start at general pages, move to information related to the whole of the UK, then ‘drill down’ via country and county to Parish or Registration District.  If you want to know where parish records are held or the address of the local Registrar (it’s usually cheaper getting BMD certificates direct from them!) or how to contact the local Family History Society you’ll find it all here.
You’ll find links to most of the genealogy web sites you need from Rootsweb and Genuki but there are useful new sites springing up all the time, as dedicated enthusiasts give up their time to transcribe passenger lists of immigrant ships, census records etc. 

 Perhaps the most ambitious project is Free BMD where they are attempting to transcribe 100 million registrations for England and Wales pre-1900 – so far they’ve transcribed several million, but don’t expect to find all your ancestors there just yet.  Perhaps you could lend them a hand?  See http://freebmd.rootsweb.com

Arguably the most famous site is that operated by the Church of the Latter Day Saints (Mormons).  Although their prime motivation is associated with their own beliefs, genealogists everywhere owe them a debt of gratitude for the vast resources they have poured into research.  Their web site at http://www.familysearch.org is the way in to their vast database called the IGI.  From October 2002 they have added online access to the 1881 census of the UK, plus the 1881 Canada and 1880 US censuses.  (Be aware that getting the most out of the IGI requires some know-how and experience.  You will also need to understand their system of Batch Numbers to narrow down the millions of records to specific Parishes.   http://freepages.genealogy.rootsweb.com/~hughwallis/IGIBatchNumbers.htm#Page  is a site with a database of Batch Numbers and good explanations of the system.) 

And if you find that the paper trail has reached a dead end, you can often make surprising progress via DNA testing.  Possibly the best value, biggest database and most comprehensive reports are available through

A Hotch-Potch of other genealogy links

National Archives   http://www.nationalarchives.gov.uk

Encyclopedia of British History  http://www.spartacus.schoolnet.co.uk/Britain.html

Methodist sources http://rylibweb.man.ac.uk/data1/dg/text/method.html#general

Preserving Old Photographs http://www.geocities.com/Heartland/6662/photopre.htm

Births Deaths Marriages for New Zealand http://www.bdm.govt.nz/

Australia (Victoria) Immigration Indexes  http://www.prov.vic.gov.au/

West Sussex Record Office  http://www.westsussex.gov.uk

S & N (Genealogy supplies retailers) http://www.genealogy.demon.co.uk/

First names (with origin & meanings) http://www.babynamer.com/

Detailed Notes about the UK Censuses and how they were taken http://www.staffs.ac.uk/schools/humanities_and_soc_sciences/census/cebs.htm

The Online Family History Fair http://www.genfair.com/

NB – The Internet is always changing, so if any of these links fail to work, use a search engine to track down the new location for the information