I've found certain sites managing their links through some third party...they are called by the name link providers and the like.. Most of these sites have a form where they ask to submit link information (url, title, description) and then add the link within a couple of days after reviewing it..
Interestingly, some of these forms are automated..i.e; once you submit your site with your info.. they link gets added automatically.. Again there are a few sites whose link exchange programs are automated but they are maintained by the site itself and not through third parties
I justed wanted to know that whether these links have quality.. Are they treated like ordinary link? or SPAMS? I don't really have much idea regarding these.. please throw some light
If the site that you want a link from is relevant to your site and has similiar links on, then its more or less a pretty good site to be linked from. Other factors about the other site like content, page rank, its not just a directory/bunch of links, its a real website are also a part in whether or not the site is of any use to your search engine rankings.
Generally the ones with no automation, i would avoid, anyone can submit any site to it, not worth adding your name to a list that could include links to dodgy websites and the like.