This will be a great topic of discussion.
I am going to start by giving my 2 cents about reciprocal linking., cross-linking, and 3-way linking to related websites.
for future reference from this point on when i say linking it will mean all three.

YOU should already know that linking to UN-related websites (that serve NO purpose for your website) in order to get an extra backlinks is a BIG NO-NO!!!
In the end it will only hurt you. I understand when you have a NEW website that you are eager to attain as many backlinks as possible (even myself have fallen in this category) BUT RESIST the temptation.

NOW your saying whats the harm in reciprocal linking, cross linking and 3 way linking to related websites?
Ask yourself this.
IF Google didnt place any ranking factor in your links... Would you still link that same website. IF your answer is YES! Then go right ahead.
If your answer is NO! Then guess what... DONT!
another good qualifier to ask yourself is would you just one-way link that website?
If your answer is Yes! Again then go ahead,
If your answer is NO! Then again..DONT!
and the final last question which probably should be the first is?
Does adding this website benefit the visitors coming to my website?
again, if your answer is Yes! Go ahead,
If your answer is NO! Then again..DONT!

If I have a website about leasing apartments at the University of Texas in Austin why would i be linking to a real estate website that does vacation rentals in Ohio?
How does that help ANY person who is visiting my website.
IT doesnt, and i know that.
I only did it because, at some point in time i convinced myself or someone convinced me that it was because we are "related topics" that we should link to each other.

Umm-no!

Now if the University of Texas in Austin (hint..hint..)
as well as T.R.E.C. (Texas Real Estate Commission)
or even
The Triangle Apartments in Austin wanted to do any type of linking strategy then absolutely i would.
Why? Because any of these potential link partners would serve beneficial to the people that are visiting my website!
As a matter of fact, I HAVE one-way linked the University of Texas in Austin AND T.R.E.C.


Bottom line, YES link to related websites BUT also make sure they are beneficial to the visitors of your websites.
IF you do real estate in Colorado, and you want to link to other Colorado based real estates then go ahead.
As a matter of fact.. Go ahead and link to ANY website as long as it benefits the visitors of your website, because ultimately "the user experience" is what they are there for. Improve THAT and I guarantee you that Google will reward you more than any linking strategy.

Signing off!