A well loved feature of past British BBC election night coverage has been the swingometer - which was used to calculate how many seats the various parties would get. The BBC archive has just released a fascinating collection of clips. These cover the period of the 1960s to Peter Snow in 1997
If you are more interetsed in calculating the results for this year's election, try the current online BBC swingometer
The Times newspaper also has an election seat interactive map.
More sophisticated is the Electoral Calculus website which uses scientific calculation to predict outcomes for individual constituencies and the nation as a whole.
The UK polling report is also useful for pulling together in one place recent polls from the main agencies, giving a snapshot of the current mood.
Finally the ever reliable Richard Kimbers Political science resources website has an index of 2010 websites. There is a section for political polls and betting where you will find links to the main online betting agencies should you want to lose (or win!) some money!