No company

YBHTM - yBook HTML File
YBTXT - yBook Text File
YGN - yGen Project File
YWP - yWriter Project
YCT - YahELite Chat Transcript
YPF - YahELite Configuration
YDL - YAODL 3D Scene Description
YHF - Your Honey Frame Shape File
YMA - YMAG Center Data Exchange File
YWEMANIFEST - Yahoo! Widget Manifest File
Y - Desktop Color Separation Specification Yellow Layer
Y - Yacc: Yet Another Compiler-Compiler Grammar File
Y01 - Paradox Secondary Index
Y02 - Paradox Secondary Index
Y03 - Paradox Secondary Index
Y04 - Paradox Secondary Index
Y05 - Paradox Secondary Index
Y06 - Paradox Secondary Index
Y07 - Paradox Secondary Index
Y08 - Paradox Secondary Index
Y09 - Paradox Secondary Index
Y2 - Plugh!
Y64 - Commandos 2 Game Mission
YAB - YaBasic Source
YAL - Arts & Letters Clipart
YBK - Encarta Yearbook
YBM - Face Bitmap
YBS - YBS Compressed Archive
YC - YAC Compressed Archive
YDK - Yusuf Data Recovery
YENC - yEnc Encoded File
YG0 - Paradox Secondary Index
YG1 - Paradox Secondary Index
YG2 - Paradox Secondary Index
YG3 - Paradox Secondary Index
YG4 - Paradox Secondary Index
YGO - Paradox Database-related File
YIF - Graphic
YLT - TheWord & Bible Companion Young's Literal Translation Bible
YMACRO - YaHoE File
YMAP - Ygnius Computer Aided Thinking File
YMP - MicroSim PCBoard Mapping File
YN - Audio Utility Tuningwrench Compressed File
YNC - yEnc Encoded File
YNX - Seqmax Seqprest Compressed Audio File
YPK - MicroSim PCBoard Mapping File
YPL - Yahoo! Player Playlist
YPT - Cryptic File
YSP - Bitmap Graphic
YUV - Color Space Pixel Format
YUV3 - CCIR 601 2:1:1 Bitmap
YYC - Wave Sapphire Distribution File
YZ - YAC Compressed Archive File

Adobe

YEL - Yellow Color Separation

Ag Leader Technology, Inc.

YLD - SMS Yield Monitor Data File

Amiga

Y - Amiga Yabba Compressed Archive

Atari

YM - Atari ST YM2149 Module/Song

BinaryTechnology

YZ1 - DeepFreezer Compressed Archive

GGNetworks

YGM - YahooGroupManager Ver. 1.x Database
YGM2 - YahooGroupManager Ver. 2.x Database

Konami Group

YDC - Yu-Gi-Oh! Power of Chaos Card Deck

Ruby on Rails Project

YML - Ruby on Rails Database Configuration File

Techsail

YML - Sailfish Yacht Analyzer XML-based Data File

Westwood Studios

YRM - Command & Conquer Yuri's Revenge Unofficial Multiplayer Map
YRO - Command & Conquer Yuri's Revenge Official Multiplayer Map

Yahoo!

YMG - Yahoo! Messenger
YPS - Yahoo! Messenger