Cookie Control is a free, configurable app designed to help your site comply with EU and UK legislation on cookies. Under the legislation websites are required to obtain consent before saving any non-essential cookies (yep, that includes Google Analytics), onto the user's machine.
Cookie Control has two functions:
1) Provides an instantly recognisable indication that cookies are being used by the site
2) Provides a user interface enabling users to accept cookies
The supporting documentation also provides information on how to audit your site for cookies, update your privacy policy, and adapt your code for complete compliance.