Droppy
Simple & light-weight roll-over navigation menu.
http://onehackoranother.com/projects/jquery/droppy/
by Jason Frame

jQuery Easing Plugin
GSGD to give advanced easing options.
http://gsgd.co.uk/sandbox/jquery/easing/
by George McGinley Smith

LavaLamp
A menu plugin for jQuery with cool hover effects.
http://gmarwaha.com/blog/?p=7
by Ganeshji Marwaha

DD_belatedPNG
Medicine for your IE6/PNG headache!
http://www.dillerdesign.com/experiment/DD_belatedPNG/
by Drew Diller

CurvyCorners
Generates rounded corners for your boxes.
http://www.curvycorners.net
by Tim Hutchison

Smart Columns w/ CSS & jQuery
Generates liquid column for object fitting.
http://www.sohtanaka.com/web-design/smart-columns-w-css-jquery/
by Soh Tanaka

idTabs
It makes adding tabs into a website super simple.
http://www.sunsean.com/idTabs/
by Sean Catchpole

jTypeWriter
Typewriter effect without the use of flash.
http://www.dummwiam.com
by Nikos "DuMmWiaM" Kontis

Automatic Image Slider
html & CSS based image slider.
http://www.sohtanaka.com/web-design/automatic-image-slider-w-css-jquery/
by Soh Tanaka

swfobject
Standards-friendly method to embed Flash content.
http://code.google.com/p/swfobject/
by Bobby Vanders Luis

Overflow Bypass Technique
Block overflowing useless overflow:hidden.
http://naradesign.net/wp/
by Chan-Myung Jung

Login UI
Static style login UI from NULI UIO Factory.
http://html.nhndesign.com/ui_common_login
by Jae-Sueng Joo

CSS3 Reference
Reference CSS3 techniques from Naradesign.
http://naradesign.net/wp/
by Chan-Myung Jung

IE8 Campaign
Web browser upgrade guiding system from NHN.
http://campaign.naver.com/goodbye-ie6/problem.nhn
by NHN

Country Flag Icons
240+ Flag icons in every size you need.
http://www.gosquared.com/liquidicity/archives/1493
by GoSquared

Design Select Box
Simple jQuery select box
http://html.nhndesign.com/ui_pattern_etc
by Chan-Myung Jung