Here are a couple that I know:
http://www.primalink.nl/
http://www.phpld.nl/

Happy you are here. I hope you have a good time with us.

Welcome, I hope you have a good experience here.

Excellent, glad you got it solved.

This is actually included in most 3.3 templates now. You can check the smarty code in the left_side.tpl and then also look for the reference to statistics in init.php. Good luck. :)

Thanks, and we have just now released the beta to phpLD users, and hope to go final in a week or two.

We now have a preview with some screenshots and other information about phpLD version 3.3 that will be released in Beta in the next few days.
phpLD 3.3 Preview...

Thanks for recommending phpLD. Yes, both the free and paid versions can be configured to require reciprocal links (or not). You can see an example here:
http://www.businessplexus.com/
And this is...

I'm new and don't want to seem rude, but I have found the advertising to slow down the site a bit.

This one really made me think...
(someone shared this definition with me)

What is the definition of Insanity?
Answer: Doing the same thing over and over and expecting a different result.
...

I've even run some experiments and found they both do just as well. If you are really concerned both about SEO and the ability to be able easily make changes in the future you could also consider...