Ubuntu
对应GNOME桌面：

Windows --------- Ubuntu

Internet Explorer（及其衍生版） --------- Firefox（及其衍生版）, Opera, Epiphany, Midori, W3M,

Microsoft Office --------- OpenOffice.org, 永中office(EIOoffice)，Google Docs, GOffice(中文不推荐）

QQ--------- Pidgin，EVA, LinuxQQ, LumaQQ

Winamp -------- Xmms, Audacious

Photoshop --------- Gimp(Cinepaint)+Inkscape 或 Pixel

AIM, ICQ, MSN, Yahoo!, Jabber, IRC instant messaging --------- Pidgin

Skype --------- Skype，openwengo，voipstunt，Ekiga

Word Pad (or notepad) --------- Gedit, nano, vim1, medit, leafpad, mousepad

Windows Media Player --------- Totem, Mplayer, Gxine，SMPlayer, VLC

iTunes --------- 播放音乐:
-----------------------Exaile
-----------------------------Rhythmbox
---------------------- iPod Syncing
--------------------------------Gtkpod

ID3 tag editor ----------------------- easytag

MIRC -------- Xchat

Premiere (Movie Editing) --------- kino, CINELERRA

Bittorado --------- Bittorado

Dreamweaver --------- KompoZer

CDex ---------- Sound Juicer

Nero -------- K3b, Brasero, Nero3 For Linux

Outlook Express --------- Evolution, Thunderbird, Opera

Partition Magic --------- Gparted

eMule ----------- aMule, mldonkey

DC++ -------------- Valknut

BT下载 ------------ Azureus, 奔流

普通下载--------------- D4X, wget, Multiget, Axel, Gwet, mldonkey

regedit -------------------- gconf-editor

Adobe Illustrator ------------ Inkscape

Remote Desktop Connection ------------ Terminal Server Client

Windows Explorer ------------- Nautilus, Thuar, Rox-filer, Pcman filer

Windows Picture and Fax Viewer ------------ Image Viewer (Eye of GNOME)

Paint ------------- Jdraw, GNUPaint

Kubuntu
KDE桌面:

Internet Explorer --------- Konqueror, Firefox, Opera

Microsoft Office --------- OpenOffice.org, Eioofice, Google Docs, KOffice(中文不推荐）

QQ--------EVA, QQ, Pidgin

Winamp -------- Amarok

Photoshop --------- Gimp+Inkscape

Aol Instant Messenger --------- Kopete

Word Pad (or notepad) --------- Kwrite

Windows Media Player --------- Kaffeine, Smplayer

iTunes --------- -播放音乐:
-----------------------------Amarok
-----------------------------Juk
----------------------iPod Syncing
--------------------------------Gtkpod

Premiere (Movie Editing) --------- kino

Bittorado --------- Bittorado

BT下载 ------------ Azureus, 奔流

普通下载--------------- D4X, wget, Multiget, Axel, Kwet

Dreamweaver --------- KompoZer

CDex ---------- Kaudiocreator

Nero -------- K3B

Outlook Express --------- KMail, Thunderbird, Opera

Partition Magic --------- Qparted

-------------------------------------------------------------------------------------------------------------------------------

如果还有上面没有提到或者更好的，欢迎在下面跟帖回复。。

感谢dennis175 提供：
QQ游戏可以用蓝迪游戏 来代替（虽然人和游戏不是太多）凑个数
PS：WINE也可以运行一部分

感谢freshfish 提供：
最近发现一个可以代替Protel的软件：KiCAD，搜索一下就可以了。是法国人做的，GPL发布，最棒的是可以生成三维图！缺点就是这类软件的通病了：库文件不够全。另外，文档做的不错，正在学习中。

感谢solotim 提供

我的推荐
Explorer ----------------------- Thunar(within XFCE)
IE ----------------------- SwiftFox(Firefox)
GoogleTalk ----------------------- Jabbin(VoIP supported)
MSN ----------------------- aMsn(VoIP/Video supported), www.meebo.com (webmessenger: GT,MSN,Yahoo,ICQ etc. supported)
QQ ----------------------- www.imhaha.com (webmessenger: QQ,MSN etc supported)
EMail Client ----------------------- Sylpheed, Claws-Mail(两个轻量级的邮件客户端，比Thunderbird来的快多了)
Notepad ----------------------- MousePad(既然有人提，还是列出来这个，其实偶尔还是有用的)
龙卷风收音机 ----------------------- Streamtuner (比ljf强大多了)
Ultraedit ----------------------- GEdit(这个还是要逊色些)
EBWin ----------------------- EBView(查日文字典的), Stardict
MS Office ----------------------- OpenOffice, EIOffice, GNumeric(表格)
TVKoo, PPLive ----------------------- Sopcast
acrobat reader ----------------------- Xpdf
acdsee ----------------------- GQview

FROM：http://forum.ubuntu.org.cn/viewtopic.php?t=20859