delete unnecessary files from the system

bleachbit

delete unnecessary files from the system

BleachBit deletes unnecessary files to free valuable disk space, maintain privacy, and remove junk. It removes cache, Internet history, temporary files, cookies, and broken shortcuts.
Main screen of unity-control-center

unity-control-center

utilities to configure the GNOME desktop

tool to take pictures and videos from your webcam

cheese

tool to take pictures and videos from your webcam

A webcam application that supports image and video capture. Makes it easy to take photos and videos of you, your friends, pets or whatever you want. Allows you to apply fancy visual effects, fine-control image settings and has features such as Multi-Burst mode, Countdown timer for photos.
Microsoft Windows Compatibility Layer (Binary Emulator and Library)

wine1.6

Microsoft Windows Compatibility Layer (Binary Emulator and Library)

mail/news client with RSS, chat and integrated spam filter support

thunderbird

mail/news client with RSS, chat and integrated spam filter support

Thunderbird is an mail client suitable for free distribution. The goal of Thunderbird is to produce a cross platform stand-alone mail application using the XUL user interface language. It supports different mail accounts, no matter of the used protocol like POP(s) or IMAP(s), has an integrated learning Spam filter, and offers easy organization of mails with tagging and virtual folders. Also, more features can be added by installing extensions.
Graphical package manager

synaptic

Graphical package manager

Synaptic is a graphical package management tool based on GTK+ and APT. Synaptic enables you to install, upgrade and remove software packages in a user friendly way.