iWallpapers is a free application from BigBoss on Cydia.
It will permit you to visualize, download many wallpapers for your iPhone or iPod Touch, data base of 10 000 pictures.

UnlimVideos is a free application from the dev Enea Gjoka, creator of UnlimTones, available on BigBoss.
This application will permit you to watch videos in streaming or download videos like TV series, films (US service).

SBSettings is a MUST-HAVE tweak.
It will permit you to access quickly from your Springboard to enable/disable many fonctions like bluetooth, wifi, 3G, etc...

When you turn on an Exchange email account, iPhone auto-locks the screen so that a password is needed every single time you slide the slider. That is pretty annoying. This tool gets rid of that, so that you don't have to enter a password every time. Note: this means that essentially this gets rid of password protection completely from your iphone springboard main screen.

Winterboard is a MUST-HAVE application that every jailbroken iPhone must have. It permits you to customize your Springboard and add many tweaks.

Backgrounder is a tweak available on Cydia and necessary for all jailbroken iPhone or iPod Touch.
It will then permit you to manage multitasking (you can have several applications running at the same time).

Make third party browsers your default!

MyWi is to Create a WiFi HotSpot with a press of a finger! Wherever you are - you can connect your laptop or other mobile device to your iPhone easily!

Update : MyWi 4.o Released 

iFile is a file manager runnning under user root. It allows fast navigation through the iPhone file system. You can create, delete, copy, cut (move), paste or zip multiple files or directories at once. Viewers for various file types are included, e.g. movies, images, sound, text, HTML, plists, Microsoft and Apple types, PDF, various compressed formats. PDF and image files can be viewed at large zoom scalees. You can directly jump to specified pages in a PDF.

You love your iPhone as much as we do? You text all the time? Want more features? Then biteSMS is for you, with lots of extra features like smileys, Quick Reply, Quick Compose/Quick Call, Privacy, a character/SMS counter and much more!

Pulse  is now available on iPhone. With this program you can read all the news of our favorite blogs directly from a single application.

If you want to save web pages to read about Mac and iPhone using iBooks, though not connected to the Internet ( Offline ) , there is a simple and quick solution for you.

We found TomTom app for iPhone fantastic, and this is speaking as an owner of a dedicated navigation unit. The interface has the usual TomTom ease of use, configurability of map color schemes and voices, and good reliability. The spoken instructions are timed just right. Also a big positive for me; traffic camera warnings. Driving through the UK where traffic cameras are everywhere, and the fines are big, the traffic camera warnings saved me the purchase price many times over.

In addition to housing Bumper Apple, there is now marketing a product which, in intent, should solve problems related to lack of reception on the iPhone 4 (problems, however, we have seen to be common to many other smartphones and not affecting the quality of call).

A Japanese user, tired of not being able to use the iPhone as a classic PDA, found an original solution ...

The app is developed by Mozilla, and will allow users to synchronize bookmarks, history and open tabs between their computer(s) and the iPhone.

Mozilla just posted a new page on their site where they are announcing that the app is on its way to our iPhones ( probably right now Apple is reviewing the app). They also released a new commercial , presenting the app and showing how can we use it.

iH8sn0w has just released Sn0wbreeze V1.6.2 to Fix Youtube issues and iTunes Restore Errors, Sn0wbreeze allows you to Jailbreak iPhone 3GS (Old Bootrom Only), iPhone 3G, and iPod Touch 2G on iOS 4 for Windows Users.