Which Distro is Right for Me? - a concise guide on Linux.org to the more common Linux Distros
DistroWatch.com - a massive directory of available and historical Linux Distributions. Provides popularity charts and other general data.
Debian - one of the most thoroughly tested Linux distributions
Linux Mint - a derivative of Ubuntu that many prefer
Turnkey Linux - ready-built Linux application servers for many different purposes
LibreOffice - a powerful Office suite compatible will all commonly used office documents
GIMP - a hugely capable image editor for graphic design, photo editing and illustration work
Inkscape - professional drawing application for working with SVG and PDF documents
MuseScore - create, play and print sheet music
W3Schools.com - the best starting place for tutorials and reference data on all web technologies
Mozilla Developer Network - another excellent source for tutorials and reference material on web technologies
PHP.net - PHP scripting language, on-line documentation and help.
MySQL.com developer site - The widely used database server, on-line documentation and help.
W3C HTML validation service - or checking your HTML markup.
W3C CSS validation service - for checking your CSS files.
Linux User Groups
lug.org.uk - Home of the UK Linux User Groups
Powys Linux User Group - The site includes lots of useful information.
Shropshire Linux User Group - The site includes lots of useful articles, particularly for the beginner.
Other useful resourcesThe Story of Linux - video made for the 20th anniversary of Linux in 2011