Portable apps come handy when you are no where near your own Mac but still need to use some of your favourite applications. How can you use an application on someone else's Mac even if it's not installed on it? Portable apps.

Here's a list of some essential portable applications for Mac OS X that you can carry on any portable device such as USB thumb drive, iPod, portable hard drive, memory card, etc. All of these apps can also be saved in your local hard drive so that you can use the application without the need for installation.

Portable Firefox OS X (Internet)

Portable Firefox OS X allows you to carry your bookmarks, extensions, history, cookies, and saved passwords with you along with the convenience of Mozilla Firefox Web browser. It will take up just 57MB space on your USB device. If you are really big fan of Safari Web browser, you can also have it as your Safari Mac OS X portable app.
Download: PortableFirefox_3.5 (22.8M)

Portable Thunderbird OS X (Email)

Portable Thunderbird OS X comes handy when you want to carry your inbox with you. It allows you to take your email, address book and account settings with you. It will require 60 MB of space on your USB drive.
Download: PortableThunderbird (22.4M)

Portable Adium (Messaging)

The Mac OS X portable version of Adium is a multi-protocol instant messaging application that enables you to carry contact list, emoticons, message stiles, plugins, scripts, sound and users. Portable Adium supports AIM, MSN, Jabber, Yahoo, etc. It will require 65 MB of space on your drive.
Download: PortableAdium (26MB)

Portable AbiWord OS X (Word processing)

Portable AbiWord OS X is compact version of the light-weight cross-platform word processor. AbiWord is able to read and write all standard document types, such as .odf (OpenOffice.org), .doc (Microsoft Word), WordPerfect and Rich Text Format. It will consume some 35 MB of space on your drive.
Download: PortableAbiWord (9.5M)

Portable OpenOffice.org OS X (Office suite)

Portable OpenOffice.org is an office suite complete with word processor, spreadsheet, presentation tool, drawing package and database. It will need slightly more space on your drive, 430 MB.
Download: Portable OpenOffice (127.1M)

Portable Nvu OS X (Web designing)

Portable Nvu OS X allows you to design and manage your websites on the go.
It will use up 35 MB of space on your drive.
Download: Portable Nvu (12.0M)

Portable Check Off

Portable Check Off is a to-do list application in your portable device.
Download: Portable CheckOff (0.4M)

Portable Cyberduck

For designers and techies, or if you need file transfers, Portable Cyberduck is a FTP and SFTP (SSH Secure File Transfer) browser with an easy-to-use interface.
Download: Portable Cyberduck(9.9M)

Portable Gimp.app

GIMP is the most popular alternative of Photoshop. This image manipulation application is available as portable app for Mac OS X.
Download: Portable GIMP for Mac (87.5M)

Portable Inkscape OS X

Portable Inkscape OS X is portable version of vector graphics editor Inkscape. It requires Apple's X11 which is included in the "Optional Installs" package on the OS X install disk.
How to install X11 on OS X 10.4 (Tiger)
Download: Portable Inkscape (24.6M)

Portable VLC OS X

VLC is one of the best all-rounder music player, and the portable version of VLC multimedia player for Mac OS X allows you to carry it with you on any portable device.
Download: Portable VLC (20.9MB)

Portable Audacity OS X

Portable Audacity OS X packages the Audacity audio editor packaged as a portable application.
Download: Portable Audacity-OSX

Portable RSSOwl OS X

Portable RSSOwl OS X is a portable newsreader.
Download: Portable RSSOwl (5M)

SyncPAppX

When you have an application installed on your own Mac, you would like the portable application to be have exactly the same settings for the best comfort of use. SyncPAppX.app syncs the preferences between portable and local applications. This means that your local preferences will be the same as Portable ones.

FSuite

For all those lazy bummers, FSuite (700MB) is a collection of over 30 useful portable applications (office, graphic, audio, video, Internet, developer tools and games). Just download one file to get your collection of portable applications for Mac OS X. Many of the above mentioned apps are available on FSuite Portable Apps.