Check this link out: http://www.engineeringtoolbox.com/p-id-drawing-d_1639.html
It's a google doc drawing that has symbol libraries built in to it. An absolute must-have for quick and dirty P&ID's. Another option is Microsoft Visio for P&ID's...if you already have it.
Tony, thanks for sharing.
Please contact me at email@example.com for our P&ID solution on SolidWorks.
We have standard 2d block libraries prepared, you can simply drag & drop and make it intelligent P&ID diagram in SolidWorks.
You will get all the deliverables automatically like line list etc.