I don't know of any scripts like that but if you were to store the reviews on a database, it wouldn't be that difficult to select all the entries alphabetically.
For instance, if the field(column) storing the site name is called
site_name and a letter of the alphapet was passed to the script to a variable called
$startsWith... the select statement might look like this:
Then if you were searching for 'A' sites, the LIKE clause of your sql statement would be
LIKE 'a%' meaning anything beginning with 'a'.
Hope this is helpful.