With this simple mod you can include any field from the link table in the URL of the details page. So instead of having a URL that looks like http://rakcha.com/phpld//link-18.html you can have it look like
http://www.rakcha.com/phpld/Paid_Web_Directories/enQuira-directory-25.html

Implementation:
in link.tpl
FIND:

{$smarty.const.DOC_ROOT}/detail/link-{$link.ID}.html

REPLACE BY (this is 1 line, there is no line break!):

{$smarty.const.DOC_ROOT}/{$link.CATEGORY_URL|escape|trim}
{$link.TITLE|escape|trim|replace:' ':'-'}-{$link.ID}.html

in detail.php
FIND:

preg_match ('#(.*)link(_|-)(\d+)\.htm[l]?$#i', request_uri(), $matches);

REPLACE BY:

preg_match ('#(.*)(_|-)(\d+)\.htm[l]?$#i', request_uri(), $matches);

The following line should be 

$id = (!empty ($matches[3]) ? intval ($matches[3]) : 0);

So if you have $matches[1] replace it to $matches[3] for both instances.

in .htaccess
LOCATE the code between <IfModule mod_rewrite.c> and </IfModule>
REPLACE BY:

# URL rewrite rules
<IfModule mod_rewrite.c>
RewriteEngine On

#Make sure RewriteBase points to the directory where you installed phpLD.
#Example: "/phpld" if your installation is in a "phpld" subdirectory.

RewriteBase /

##Latest Links Rewrite
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^latest-listings\.htm[l]?$ index.php?list=latest [QSA,NC,L]

##Top Hits Rewrite
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^popular-listings\.htm[l]?$ index.php?list=top [QSA,NC,L]

##Latest Articles Rewrite
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^latest-articles\.html$ index.php?list=latestarticles [QSA,NC,L]

##Pagination Rewrite
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule (.*)page-[0-9]+\.html$  index.php/?p=$2 [QSA,NC,L]


##Article Page Rewrite
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule (.*)articles/article-(.*)\.htm[l]?$ article.php [QSA,NC,L]
   
##Details Link Page Rewrite   
RewriteRule %{REQUEST_URI} !page-[0-9]+\.html?$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^(.*)\.html$ detail.php [NC,QSA,L]


##Category redirect
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^(.*)$ index.php [QSA,L]
</IfModule>

That’s it, you are done!

Extension: If you want to use any other field of the PLD_LINK Table, say you have a custom field for keywords named KEYWORDS, you can add {$link.KEYWORDS|escape|trim|replace:' ':'-'} to the URL.

PS: If you want to convert the added fields like $link.TITLE to lower case, you will have to add strtolower to it. The URL becomes:

{$smarty.const.DOC_ROOT}/{$link.CATEGORY_URL|escape|trim}
{$link.TITLE|escape|trim|strtolower|replace:' ':'-'}-{$link.ID}.html

PS2: To redirect old pages to your directory home, add the following in .htaccess

RewriteCond %{REQUEST_URI} ^(.*)/detail/link-(.*)\.html$
RewriteRule ^(.*)$ http://www.yourdirectory.com/ [R=301,L]

It is not possible to redirect old pages to new pages as the listing title or category are not available at the htaccess level. However this will not cause a problem as old pages will be promtply deindexed thanks to the 301 redirect to the homepage, and new pages indexed without causing duplicate content.
ENJOY!