From what I've read, there are no GOOD link exchange sites.
SEs consider them link farms and could blacklist your site for using them.
Yahoo & Google both mention it on their sites.
They give imphasis on inboud links from good ranking sites of the same topic as yours.
Any form of link exchange is likely to be filtered as marketing links. Natural inbound links, ones with variety of text, different domains and links within paragraphs of text are mostly valued. Even inbound links saying "Jonny Bloggs website" a thousand times will be seen as marketing. The best links come from article references. Post useful information and people will naturally link to it in a variety of ways.
I have written an automated link exchange module for a php site. It can intergrate in any php application. Though it doesnt verfiy links on its own it. Can any point me in the right direction for link verification code?