Well I am webmaster on a few sites, lets say 10, and they all link to eachother so quite a good PR. But now I heard that 3 way links do it better, is that true? Is it better to remove a link per site so that each site generates a one-way link? Would that increase my PR? Is it worth it? (because right now the link is actually be used as well )
I think if your doing good now, "don't fix it if it aint broke". Long term, I think you're going to find that G's algo will devalue two way / reciprocal links. It just makes sense. You vote for me and I vote for you, in effect, they cancel each other out. If you vote for me and I vote for billy bob, then both votes are more valuable. Of course billy bob can vote for you. But I don't think in G's algo, that such a link structure would be devalued. Just my .02¢
If you own the 10 yourself then 3 way is definitely a lot safer because of the risk of the Host Affiliation filter. If G finds out two sites belong to the same organisation (either through shared IP or simply because they know) then they will treat the two as one basically removing up to 50% of your SERP rankings. Excessive two-way crosslinking will definitely trigger them to have a look at one point. 3 way will keep inter-host-linking a safe practice. BTW: use [quote equal-sign Username] to credit the quote.
It has never been proven that one way links have more weight than reciprocal links. I have numerous #1 listings based on reciprocal links for very competitive keywords. I think it is more important where the links come from and how closely matched the theme of the your site matches the theme of the site that linked to you. If 25 sites all link to you using anchor text "baby strollers" and they are all baby related sites, Google will think you are more relevant for "baby strollers" than the site that has 25 links with the anchor text "baby strollers" coming from gambling and viagra sites.