I am a great fan of Ubuntu. Have tried several times to completely migrate my desktop environment from Windows to Ubuntu. But lack of patience can’t stick to Ubuntu. This time I have successfully migrate my desktop environment from Windows 7 to Ubuntu 10.04 LTS.

Internet Browser
For regular day to day operations & office usages I am heavily dependent on internet. There is no alternative of good internet browser. I do prefer Google Chrome & Mozilla Firefox. Both of them are easily available in Ubuntu.

Document Editor
In Ubuntu I am using Libre Office. It has all the features available in MS Office. You can use OpenProj or ProjectManagement as alternative of MS Project.
Email Client
Officially use Lotus Notes. Lucky enough that debian version of Ubuntu is also available in Ubuntu. Bellow is the good link to install Lotus Notes in Ubuntu:
Mozilla Thunderbird also a good email client if you use imap/pop3 email service.
Pidgin is a good alternative of all the messengers. You can use it as alternative of google talk, msn messgner, yahoo messenger. Skype debian version is also avialable for Ubuntu.
32 bit version Ubuntu doesn’t support more than 3 GB RAM. But if you have more than 3 GB RAM you can swithch to 64 bit Ubuntu or you can install Physical Adress Extension (PAE) aware kernel under 32 bit Ubuntu to overcome Ubuntu 4 GB RAM limitation. Bellow is a good link where you get how to overcome Ubuntu 4 GB limitation & soltuion:
Image Editor
I am great user of Adobe Photoshop & Adobe Lightroom to edit my SLR RAW images. There are few good alternative of Adobe Lightroom. I prefer Darktable & RawTherapee.
imageScreenshot of my Ubuntu Desktop

20 Most Highly Rated Applications to Install from Ubuntu Software Center
Bellow is a good site which give the source & features of 20 most highly rated application which you like to install in your Ubuntu Desktop:
I personally use lot of VM distribution. Oracle VM Virtualbox is a great alternative of Vmware Player.
Still I don’t get a good alternatives of iTunes. Have tried it with wine, but performance is not that satisfactory.
If you like Mac Dock, you can try Docky in Ubuntu. It’s free and easy to customize. From Ubuntu Software Center, search for “Docky”. It will be installed under Application > Accessories.