The TUC website has a lot of useful information on employment law. It includes advice on contracts of employment, dismissal, health & safety, rights for working parents, employment tribunals and more. There is a handy list of when you get which rights: which start on day one, which you have to wait one month, one year, or even two years to claim.
You can link to it by clicking here [1].
The TUC also runs a website, WorkSmart [2], with lots of useful information.