s.gd is a service that shortens URLs such as web addresses. This is useful in many circumstances (see below) e.g. in email clients that break long URLs.
For example, you can turn
http://maps.google.co.uk/maps?f=q&hl=en&geocode
=&q=louth&ie=UTF8&z=12&iwloc=addr&om=1
into :
http://is.gd/6