RF and Microwave Useful Links or Tools:

Microwaves101Includes encyclopedia of terms and acronyms, useful on-line calculators, and downloads.
RF Globalnet – Microwave Industry News, Analysis, and Technical Articles
Modelithics – Industry leading provider of simulation models for RF, Microwave, and Millimeter-wave devices.
Black and White or Color Smith Chart (PDF)
Free RF Lineup Cascade Analysis Excel Tool
Electronic Symbols in MS Word .doc format

Vendor Technical Support:

Carlisle Interconnect Technologies (Tensolite)
CML Microcircuits
Dielectric Laboratories
Gowanda Electronics
Innovative Power Products Catalog
KCB Solutions, Inc.
Linear Technology
Mercury United Electronics
Mini-Circuits Application Notes
Passive Plus Technical Documents
Passive Plus AVX/ATC Cross Reference
Pulse Electronics
RF Industries