u will need:
- LM7805 IC (TO-220 package) - pin 1 is the left most lead in the position when reading the IC's label.
- 9V battery
- 9V battery clip
- charger socket (from an old/damaged charger)
- soldering gun/iron and some lead

steps:
1. connect battery clip to battery
2. solder/connect black wire/negative terminal of battery to the middle pin/pin 2 of LM7805
3. solder/connect red wire/positive terminal of battery to pin1 of LM7805
4. connect the positive (one with stripe) wire of the charger socket to pin3 of the LM7805
5.connect the negative wire of the charger socket to pin2 of the LM7805
6. plug the socket to phone and viola!

if you have some pics of this it would help a lot because not evryone is familar with those device names.

thanks for the suggestion, here are the images:

- LM7805 IC (TO-220 package) - pin 1 is the left most lead in the position when reading the IC's label.
[Only registered and activated users can see links]

- 9V battery
[Only registered and activated users can see links]
- 9V battery clip
[Only registered and activated users can see links]

- charger socket (from an old/damaged charger)
this is the socket/plug(whatever you call it) that you plug into your phone. Cut the wire and you should see a red and black wire inside. they correspond to the black and red (or one with a stripe) wires of the battery clip. you only need the socket with some wire. Electronic shops should have this too.

- soldering gun/iron and some lead
If you dont know this tool, dont use it as it is dangerous. instead let someone else do it. Or do other methods of connecting the wires (use of clips etc.)

I've seen these portable chargers before, but how much of a charge can you get from a 9V battery? Is it enough to actually charge the phone, or just so you can use it while hooked to the 9v battery.

its so complicated,, i have one wireless mobile charger.. it use 3 AAA battery but it's useless!! it can only use for several minutes.. here it is..

that's great idea to use 9v battery with 5v regulator 7805, but 9v battery pack is only 100mA or less . how can u charge 800mA+ phone battery?
can people here post a step-up 3v circuit to 5v. it would be useful. cos AA batteries have more than 500mA.