0808 numbers are used for freephone services in the United Kingdom.
They are in the format 0808 xxx xxxx.
They are normally free to dial from a land line, however when called from a mobile phone, they are often charged at a rate typically between 14p and 40p per minute.
An exception to this is numbers in the format 0808 80x xxxx, which are reserved for not-for-profit helplines and are usually free to call from mobile phones.
More information on individual 0808 numbers can be found by browsing the 0808 number list.
Other freephone numbers in the United Kingdom are 0800 numbers and 0500 numbers.