Recently I decided to try using MiFi so that I won’t need to have another sim card to go online with my other phone.
I bought E5830 Pocket MiFi which is small that fits in my palm and can carry it around without any hassles. It has 1500mAh battery that can be used for 5 hours as I have tested it. It weighs about 90g and also has microSD slot. It can connect your PC or laptop through mini-usb cable and get connected using the built-in software Mobile Partner. I find it very easy to configure and can connect instantly.
I am now planning to buy another battery so that I can prolong the usage of this device.