If you can't find it here, maybe you find it there Dot What? The file extension database.
File-Extensions.org File extensions encyclopedia - The source for file extension information. An easy searchable database with file types, associations and info.
FileInfo.net File extensions site that has a searchable database of extensions, with detailed explanations of each file type, and suggesting programs used to open the file.
Dateiendungen German website suggesting many applications for the extensions that you are looking for.
Convert Files - File Converter Directory Resource to help individuals and businesses find the solution to their file conversion needs. Selling a converter? Get it listed here.
File Extensions with many links to the source programs.
What Is... every file format in the world
File Extensions Nice list of filename extensions, good descriptions.
Cibderf Here's a giant french database of almost 2000 file extensions. This database can be downloaded in various formats.
How to Unpack Files How to unarchive files in Unix, Dos (Windows) and Macintosh.
Filename extensions - what they mean Small list of Unix extensions.
File (de)compression, and packaging: .gz, .tar, .uu, .Z, .zip How to archive files in an Unix environment.
Data Formats and Their Sugggested File Extensions
Incomplete dictionary of filename extensions Good explanations of many filename extensions.
Multimedia-Testpage- Audioplugins und Viewer This page suggests browser plug-ins for various video formats (German).
EXTSearch - Search for file extensions Search engine for more than 1000 extensions, this site also has a bulletin board for if you didn't find the extension that you were looking for.
Filex Huge lists of extensions, MIME types and applications. The extensions database contains more than 3000 items.
List of File extensions
Microsoft Office Converters and Viewers
Graphics file formats - PC Webopaedia Definition and Links Site dedicated to graphical file formats.
Graphics File Formats FAQ Great FAQ about many graphical file formats, together with many links to image display and conversion programs for Dos, Windows, OS/2, Mac, Unix and Amiga.
Common Internet File Formats Here are some formats often found on the Net, together with some Helper apps. for Macintosh and Windows.
Wotsit's File Format Collection This site is especially interesting for programmers.
Mushinskiy's Standard File Formats Extensive descriptions of many formats.

Online conversion on the WWW MediaUpgrade Converts AVI and WAV to ASF, WM, RM, RA or MP3
BCL Computers' gohtm.com : Instantly convert document into HTML Convert PDF, RTF, TXT, DOC, XLS and PPT to HTML
InterGuru's E-Mail Address Conversions Online conversion of e-mail address lists between various e-mail clients.
Convert graphics, documents and sound file formats online free

Texts regarding file formats Smart Computing-Editorial Usefull text about repairing damaged 'office-like' and some other file formats and how to handle compatibility between different applications and versions

Magazines and (free) newsletters which have featured WhatFormat :-) The Submarine Popular russian magazine about computers
TechnoGrok
Joe's Place
Lockergnome

Interesting stuff for sitemasters #1 Internet Marketing Provides internet marketing and promotion
NetStat A very extensive free counter
The Free Site: Free Counter Services, counters, free trackers Many links with good descriptions to free counters
Anders Qvicker - AQ art & design - Free Stuff Free Images, Backgrounds etc. for your Webpage
Actonvision Internet Marketing, branding and emarketing tools
EmarketingMag offers emarketing services, Search Engine Internet directory, branding, Internet Marketing, information, and web guide

About Computers: Hardware Chip directory A lot of info about chips
Wim's BIOS Page Anything about BIOSs
Motherboards.org Start Page for Newbies. Lot's of info on motherboards
Tom's Hardware Guide. A giant base of hardware info
Inkjet Cartridges and Printer Ink Refills. InkSell.com offers genuine, compatible ink cartridges, and inkjet refill kits at 70-80% discounted prices. Free shipping on orders over $49. Laser toners and Phaser solid ink also available

About Computers: Software Chinese Kungfu screensaver.
Pc Anywhere Review - Reviews and recommends remote access software.
HotMind Software. Pioneer developer and publisher of free- and shareware Internet games and entertainment software.
Rob's Linux Homepage. Info about this free and I believe excellent OS.
Focus on Linux - Welcome from The Mining Company
Warp X - The future with OS/2 Warp
Master OS/2 Warp Update List: Undocumented Tricks & Tips
Sergey. Here you can find programs, which can be useful for all or nearly all: system utilities, mathematics and many others. Information for amateurs of Assembler (interesting procedures, guide to Assembler), Basic (several programs), Pascal (program and modules), Delphi (program, modules). Documentation. Directory of resources of Internet. Humor. Exchange by references. (only Russian)
Data Recovery - Disk Recovery, Hard Drive Recovery, Raid Data Recovery : Data and Disk Recovery from hard drives, Tapes, optical media, flash cards. Raid Arrays, Win 95/98, Win NT, Win 2000/XP, Novell, Linux, and Mac

About computers: Download Sites Go Wares Big Windows categories on this site, free- and sharewares.
ListSOFT This is a really great Russian free- and shareware site. This links to the English mirror.
Download.Com
Freeware Central
Shareware.Com

Free stuff! Answer 3 Survey Questions and Win $500!
The Amazing Free Stuff Page
ScarletWillow's Money & Cool Stuff Page
BelgianFreebies Freebees for Belgium, I guess most of them are also interesting for Holland

Interesting... Antifascist Russia This site also has some english pages against fascism and nationalism.
The Great Druids Website about Magic the gathering (Dutch).
MovieMania Good looking website on movies.
Hagerstown Users Group This is the homepage of a PC users group in Hagerstown, Maryland, USA.
The Camp Pages Many links on Genealogy, Midi's, Graphics, Games [bowling], Educational and Odd interesting information, Various Search Engines. Check it out!
Dopey's homepage. Cool website with a schoolpaper of the Zandvliet College in The Haque and some book reports. This site is partly in english and partly in dutch.
Wehkamp Veilingmeester An auction on the Web (Only for the Netherlands)
Consumentengids van Ben de Cocq Amusing consumernews (Dutch)
MoppenSite (Dutch)
Healthy Eating - Restaurants - Menus and Movie Search Restaurants - Menus and Movie Search and type in the name of Entree you like and find out which restaurant serves it
Starmonitor Affiliate Marketing and Selling Software
littlepeter.com Play free trial games and online flash games at littlepeter.com. New games will be published monthly.