Look up the position of your current IP address:

$ wget -q -O - "http://api.hostip.info/get_html.php?&position=true"
Country: UNITED KINGDOM (GB)
City: Durham
Latitude: 54.7667
Longitude: -1.566

Look up the position of someone elses IP

$ wget -q -O - "http://api.hostip.info/get_html.php?ip=212.58.226.77"
Country: UNITED KINGDOM (UK)
City: London

Another geo-location service

$  wget -O - -q "http://blogama.org/ip_query.php?ip=129.234.4.1"
<?xml version="1.0" encoding="UTF-8"?>
<Response>
    <Ip>129.234.207.232</Ip>
    <Status>OK</Status>
    <CountryCode>GB</CountryCode>
    <CountryName>United Kingdom</CountryName>
    <RegionCode>D8</RegionCode>
    <RegionName></RegionName>
    <City>Durham</City>
    <ZipPostalCode></ZipPostalCode>
    <Latitude>54.7667</Latitude>
    <Longitude>-1.5667</Longitude>
</Response>