From today you can unlock iphone 3g or iphone 2g 3.1.3 using the new tool released. The new unlock iPhone 3G 3.1.3 tool works only if your bootloader is 05.08 and you will be able to downgrade the modem baseband to 04.26 and then unlock iphone 3g 3.1.3 using ultrasn0w. For iPhone 2G you can unlock iPhone 2G 3.1.3 any type and version.
To Unlock your iPhone Online Visit:
www.unlock-iphone.org

Jailbreaking : iPhone OS uses two partitions – first on is the media partition and second one is the operating system partition. Music, movies, contacts, App Store apps etc. are stored on the media partition. This partition is usually the size of your iPhone’s memory capacity, minus 500-600MB for the OS partition. Because of the way that Apple have set up the iPhone OS, we can not do any hacking in this easily accessible partition. To hack the device, we must get into the OS partition. The OS partition, the space on the iPhone that Apple has locked us out of, is where the jailbreak  lies.

Jailbreaking is a process that allows iPhone and iPod Touch users to run unofficial code on their devices. Once you jailbreaked your iPhone you are able to download many applications, mods and hacks which are unavailable through the App Store but available via unofficial installers such as Cydia and Icy. Some of popular Cydia, Icy advantages are as on >> Winterboard (To install Themes), SBSettings (Faster Method to Manage iPhone Settings), Tricker3G (For running WiFi only App on 3G or EDGE), Cycorder (Video Recorder for iPhone 2G, 3G) and lots more.

Unlocking : Unlock iphone 3g 3.1.3 your device means to open up the iPhone’s modem to accept SIM cards from unofficial carriers. For example In the US, iPhone will not connect to any carrier other than AT&T, unless it is unlocked. Should you want to use your iPhone with another GSM carrier, you need to unlock. Just as iPhone OS controls the applications that you interact with whenever you use your phone, the baseband processor controls the modem. The baseband processor has its own, separate firmware from the main OS, called the baseband firmware. During most iPhone software updates, Apple update the baseband firmware on the device. The unlock lies in the baseband firmware, by patching out certain bytes, you can bypass the SIM check. For some devices, updated basebands can mean the inability to software unlock your phone