The Metallica clubMetallica (Official):
The Metallica portal - Metallica portal page.
The official Metallica fanclub - The place to be for Metallica fanclub members.
Metontour - Everything about Metallica on tour.

Metallica (a selection of Local Chapters):

...And Jersey For All - USA
Anger in Chicago - USA
Argentina Amber - Argentina
Battery Park - Damage Control - USA
Battery: The Chicagoland Chapter - USA
Bay Area Thrashers - USA *
Beholder Poland - Poland
Belgium Fuel - Belgium
Chapter One - The Netherlands
Damaged Switzerland - Switzerland
Danish Militia - Denmark
Don't Tread on Adelaide - Australia
Don't Tread On Austria - Austria
For Whom Metallica Tolls - Australia
Friend-tic - Luxembourg
HellasMetallica - Greece
Inter Sandman - USA, the first online Chapter of the Metallica Club.
Invisible Kids - USA *
Metal Monster - France - Russian Federation
Metalliaustria - Austria
Metallica Club Scandinavia - Sweden
Metallica Remains - Brazil
Metallica Sweden - Some Kind of Chapter - Sweden
# - UK
Metalliheads - Poland
My Friends of Missouri - USA *
Norcallica - USA
Nothing Else in B.C. Matters - Canada
OrionTurk - Turkey - Poland
Polish Scary Guys - Poland
Portugallica - Portugal
SBT Metallica Chapter - The Netherlands
Sin City Seek & Destroy - USA *
Some Kind of WV Monster - USA
St. Germany - Germany
The Belgium Devildancers - Belgium
The Chilean Horsemen
- Chile
The Finnish Chapter - Finland *
The Italian Metallibashers - Italy
The Metallica club Korea - Korea
The Outlaw Corn - USA
The Quebec's Unnamed Chapter - Canada
The UK Torn - UK
To Live Is To Die in Texas - USA
Virginia Fuel - USA
Whipping Dancerz - France
Wisconsin Whiplash - USA *

# Not officially registrated at the Metallica club at the moment / * A bit out of date.

Metallica (Other):
Alfredus´ Metallica Fan Page - Great collector page.  (Germany)
All Metallica - Page with lots of features.
Black Fuel's CD-DVD collectors guide - Great collector page.
Bootlegica - Page about... bootlegs.
Encyclopedia Metallica - GREAT Big Metallica page!.
Fredrik`s Metallica Collection -
Great collector page.
Hectors Metallica Collection - Unbelievable Metallica collectors page, all releases described! 
Insanity Palace of Metallica - Cool page with up-to-date news.
Metallica Collectors Page - The ultimate (and biggest) Metallica collection page.
(Japan) *
Metallica World - Nice Metallica page.
Metallica-online - Nice page, pictures, bootlegs,...
Metallicamp - Metallica page.
Metblackened - Great bootleg page!
(France) *
Metcolectors Metallica page - Great collector page. *
MetXXXpage - Metallica XXX Blog.
Ride Metallica Lightning - Great Metallica page. (France)
Sick'n Destroyed - Great collector page. (France)
The 4 Horsemen - Great page.
The Metallica collectors club - Metallica collectors united, great page!!.
The Metallica source - Big Metallica page with great guitar section.
Witlof's Metallica page - Great Metallica page, a lot of bootlegs.

* A bit out of date.

Other great bands:
Coldplay - Official Coldplay site.
Creed - Official Creed site.
Deep Purple - Official Deep Purple site.
Friends of Live - Official Live site.
Led Zeppelin - Great Led Zeppelin page.
Radiohead - Official Radiohead site. (a bit strange)
Sepultura - Official Sepultura site.
Slipknot - Official Slipknot page.
Trivium - Official Trivium page.

... And Guitars for All:
ESP Guitars - Official ESP site with signature models of James Hetfield and Kirk Hammett.
Guitar Lesson World - Award winning page with exercises and great online lessons.
Guitar Pro - Official website of the program Guitar Pro, great for learning songs.
Guitar World - Official website of the magazine Guitar World.
My song book - A huge site with countless Guitar Pro files.
Total Guitar - Official website of the magazine Total Guitar.