There seems to be something interesting going on between Google and the ACM archive portal.

If you visit portal.acm.org/ you see an ordinary "ACM Portal" logo. But if you visit a page such as portal.acm.org/dl.cfm?coll=por ...
the logo says "ACM Portal Google Inc", and this persists as you move through the site.

On the same page there is a "CrossRef Search" link, leading to this page
portal.acm.org/xrs.cfm?CFID=15 ...
which is described as a "9-publisher pilot for full-text scholarly research, powered by Google".

Interestingly, it seems that ACM was possibly planning to use Yahoo for this kind of thing (at least, according to Google Blogoscoped):
blogoscoped.com/archive/2005-0 ...