Pipe Dimensions:

http://www.pipingengineer.com/wallthk.htm

Piping Fittings, Welded:

http://www.weldbend.com/Fittings/fittingsindex.htm

Piping Fittings (threaded & Socket-Welded):

http://www.pennusa.com/pennpage/directory/forgecat/forgcatl.htm

Piping fittings, Misc. (Threaded & Socket-Welded):

http://www.pennusa.com/pennpage/directory/catalog/fitcat.htm

Pipe Flanges:

http://www.texasflange.com/Catalog.pdf

You do not say if you are experienced or a novice when it comes to Piping.

I suggest that you go here:

http://www.pipingdesigners.com/

You will see a line of "Blue Buttons" across the screen.

Click on each of them and read everything you see there.

You will learn a lot.