During tonight clocks will go forward by one hour throughout the EU and we shall all 'lose' one hour of sleep.
In the UK this will mean a shift from GMT [Greenwich Mean Time] to GMT+1, otherwise known as BST [British Summer Time].
In Spain, where I am now and for the next few months, clocks are already on GMT+1, otherwise known as RST [Romance Standard Time] or CET [Central European Time] and will go forward tonight to GMT+2, known here as RST+1 or CET+1.
Clocks will go back in the Autumn, in the UK and Spain and elsewhere in the European Union, on the night of 30/31 October 2010.
Information for the UK for this and the next few years is available here - see near the bottom of the page under British Summer Time.
Information for Spain for this and the next several years is available here - see near the bottom of the page under the section Cambio Horario España 1940-2010, although the years 2011 to 2015 are covered too provisionally.
There's a nice map here covering the whole of Europe in the Telefonica website I used above for the time-change in Spain. There's also a page of useful information in this same website giving details of time-changes for 2010 throughout the world.
Have a great Summer!