My links:
Submarine and ASW warfare
The Third Battle: Innovation in the U.S. Navy's Silent Cold War Struggle with Soviet Submarines - very, very recommended article about ASW in and past the cold war
Sonar and underwater acoustics:
Understanding Oceanography - fantastic page about underwater sound propagation ! very recommended !!
FAS.org - Introduction to Naval Weapons Engineering
(Underwater Acoustics, Environment, SONAR Performance I, SONAR Performance II, SONAR Systems, Underwater Weapons)
Fundamentals of Naval Weapons Systems
Sonar model and detection ranges:
Harpoon 3 sonar model
What is Known About the Character of Noise Created by Submarines?
Estimates of Submarine Detection Ranges - a bit advanced
Submarine Collision off Murmansk: A Look from Afar (optional)
Miasnikov - The Fundamental Limits of Passive Acoustics.pdf - advanced
Weapons, sensors:
Modern Torpedoes And Countermeasures
Homing instincts
Torpedos and the Next Generation Undersea Weapons
Naval Weapons of the World From 1880 to Today
Torpedoes and Mines of the Dutch Submarine Service
Russian Torpedo Armament
Russian Torpedoes for Export
The UGST versatile torpedo
Russian Torpedoes - a PDF advertisement
Russian Antisubmarine Rockets - PDF about APR family of ASW torpedos
Klub - SS-N-27 - Club-S
Submarines
Great page about russian subs - in russian... but very interesting even with use of babelfish translation to english (http://babelfish.altavista.com/). Sub monografies on right panel. Also very nice galleries of russian subs if you can find them
www.ckb-rubin.ru - Kilos
Various technical/historical:
The Naval Technical Board
Post-World War II Acoustic ASW Torpedo Development A brief history of the MK-35, MK-41, MK-43 and MK-44
US NAVY TORPEDOES by Frederick J Milford
(
Part Four: WW II development of homing torpedoes 1940-1946)
(
Part Five: Post WW-II Submarine Launched/ Heavyweight Torpedoes)
U.S. Navy's First Active Acoustic Homing Torpedoes by Tom Pelick
Submarine Warfare in the 20th & 21st Centuries : A Bibliography - very large collection, in books/history/special topics and books/submarines sections you can find many interesting books and papers with online acces, for one example:
Soto, Alberto A. The Flaming Datum problem with varying speed.... or
Adams, Brian S.. Analysis of the Effects of Energy Spreading Loss and Transmission Loss on Low Frequency Active Sonar Operations in Shallow Water or
The relationship between a submarine's maximum speed and its evasive capability :-) ...... and, fantastic find, seems to be a little extended version of
"The Third Battle", relased in PDF, I found here paragraphs that not exist in WWW version.
Utils
Radar - some info about RCS and Radar Horizon Calculator
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LoBlo's links
I've always use FAS as a good source of informaiton for american ship stats.
http://www.fas.org/man/dod-101/sys/ship/index.html
And there are a few articles on the Harpoon3 site that are interesting reads as well
http://www.harpoonhq.com/waypoint/ - very nice link

, try for example
"In Peril On the Sea: The ASCM threat and countermeasures"
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to be continued...
P.S. Some articles I had are not online anymore, or I can't find them with Google, so I put them on my personal page for you, some were saved without pictures that's why they are lacking pictures now.
Please reply once in this thread and put YOUR interesting links if you have any !