This is a very broad question and without more information on the specific need very difficult to provide an useful answer.

The various providers of RF test & measurement (T&M) equipment (Agilent, Anristu, Rhode & Schwartz, National Instruments, ...) all have very extensive application note libraries.

There are more general web sites (I sure others have other favorites)
http://www.rfcafe.com
http://www.microwaves101.com
http://www.rfglobalnet.com/forums/
.....

The IEEE has many publications and conferences http://ieeexplore.ieee.org/Xplore/dynhome.jsp
and societies that focus on RF measurements
http://ewh.ieee.org/soc/im/imnew/
http://www.mtt.org

and much, much more

perhaps you could describe the the type of measurement or problem you are having?

Not only is the device type a factor but the
desired set of measurements,
frequencies and power levels, and
Device-Under-Test (DUT) configuration (on-wafer, die, package style, ....).

I would suggest one of the commercial T&M companies (I work for one of them, Agilent) web sites and look over their application note library.  There are numerous examples provided in the app notes.

There are also a number of good books on RF device measurements to be found at Artech, Willey, ... publishers.

This is really a very broad area and there is no single answer.