Electronic Engineers Master is a large catalog of electronic components, equipment and services. All indexed, with many linlks to the manufacturers of the componenets.
http://www.eemonline.com/
An extensive list of Japanese components, including those pesky Japanese transistors including the 2SA, 2SB, 2SC, 2SD, 2SK, 2N, PN, BC, BCY, BD, BF, BS, CL, J, KM, TIP, TIS, and MAL series.
http://www.microelectr.com.hk/products.htm
Data Sheets and application notes by part number.
http://www.microlinear.com/products/index.asp
Application Notes: Complete List
http://www.national.com/apnotes/apnotes_all_1.html
for use with Spectre RF, from Cadence.
http://www.cadence.com/datasheets/rf_notes.html
The industry standard for tube specifications.
http://hereford.ampr.org/cgi-bin/tube?index=1
Flash memory-application notes.
http://developer.intel.com/design/flash/applnots/index.htm
Covers important RF subjects such as attenuators/modulators, phase shifters/ freq-translation, switches, millimeter wave components, oscillators and power measuring instruments.
http://gmcwave.com/application_note_index.html