i'm eying this one Solar cell panel having specification's as follows:

Typical Peak Power 0.55Watt
Voltage at peak power 5.5 V
Current at peak power 100mA
Length 70mm, Width 55mm

i wanted to charge a 5volt battery(connecting 3 cells of 1.5volt each so making it 4.5v) or using two of these panels to charge a 9volt rechargeable battery and then power Arduino and a RF Module(both can work easily at 5volts ,although in arduino have to plug in 5volt pin's so as to bypass the Voltage Regulator ).

What you people Suggest?, or Any better idea's or correction's you would like to make?

Definitely it's a New learning curve into MICROCONTROLLER learning ,it makes a lot easier the whole embedded process ,you will experience that if you had taken up PIC microcontroller's tried programming them in C/C++ there is a lot of mishaps and connectivity problem's that you will face initially(However will make you learn) ,but then ATmega's and PIC both are prices same more or less then ATmega based open source system's are in fact blessing's. There is a whole lot of support for it and also a person can just start and make new development's pretty fast.

@ Mowicus I was initially needing expert replies from all you people to know some cheap modules, i have found those thank you! for your Consideration, Mowicus.

@Paul S I know how to expertly operate the XBEE but the thing is cost it's atleat calling for about Rs.4,400(Two XBEE's ,One Adapter needed in any case for loading Firmware and One Breakout board, so the Minimalist Shopping list even when i'll employ one of my Arduino's to function as adapter and fit XBEE on it!) but these dumb RF Modules atleast will provide me the Basic need that is flow Information Through solid Wall's in just Rs.730 ,as you can see there's a Big Difference.

XBEE--------------------Arduino
TX or Dout to RX of Arduino
RX or Din  to TX of Arduino
+3v3 to +3v3 or VIN(i case of mini's running on 3v3 input) of Arduino
Gnd to Gnd of Arduino
Should work could be a problem with XBEE check for short cuts in Adapter or Check your Breakout board if using at all.
  

i was basically needing a cost effective way to connect wirelessly, I know XBEE Well and how to use it in any way but it's cost is a major deterrent factor that is making me avoid them ,the fact that i need one XBEE as a Main Controller and atleast one more as a router or end system coupled with the cost of ADAPTER + Breakout board .

but i have found these RF 433.9 Wireless Modules pretty Cost effective and sufficing my need for Through wall Wireless Connection.

http://tenettech.com/product.php?id_product=337 for the transmitter and i will get the receiver through the same place too.

Regards,
Nishant Sood

"If I try to read the modem parameters and firmware it fail (Failed to enter command mode, Unable to read version (ATVR) Read parameters failed)."
That's not good. How exactly are you connecting the XBee to the computer?
Have you set the baud rate correctly?

i just had the fast glimpse of whole story had read this now this many happen commonly in case of XBEE connection and the remedy i suggested is fine, as in the starting the user's may fail to adapt to the fair timing of XBEE i.e. 10 seconds may time out.

i'm talking about the XB24-Z7 one model it has this much of pin's only also if they are not needed elsewhere  , However feel free to check and if you are right then tell me too.

I wanted to wirelessly control my robot and for that wanted a pass by walls technology and also which should be cheap, i have looked deeper and found this module http://www.rhydolabz.com/index.php?main_page=product_info&cPath=130_132&products_id=454 ,i would want to connect and send commands through a bluetooth 2.0 tech. acquipped Mobile phone.

Connection should be pretty simple in my opinion just needing a tx & rx linking with the Arduino and the Bluetooth module(Module itself powered @ 3 volts [The max it can take!]) , But If i want to send the Word "Start" how i can do that using the Mobile phone?  

or if Above one is not capable then what about this BUT is Costlier than even a XBEE - http://www.rhydolabz.com/index.php?main_page=product_info&cPath=130_132&products_id=479

I think this must be an Answer - http://www.faludi.com/itp_coursework/meshnetworking/XBee/XBee_program_Arduino_wireless.html

try reseting the XBEE if it has a reset switch click and hold till the ERROR window closes or click it and then wait for 10 seconds so as to let it vanish or if XBEE's not having the Reset switch then just take the XBEE out and insert it back in the ADAPTER.

I have some people in here (India) although can ship you -

http://9circuits.com/products/asynclabs/arduino-wishield-2-0/

SPI, / The TX and RX pin's are there for the same purpose use them. 

I want to use XBEE type of Radio modules ,can you name some?

Yes, it's definitely possible it has About 10 i/o pin's and out of which 4 are analog in ,3 are digital out and 3 are digital input pin's, so definitely ON/OFF can happen , but on "BOARD" Logic is not possible, so only use a MICROcontroller only in case of some Decision making and Evaluation/Manipulation/Modification of variables etc.

You need PCB Relays, preferably powered from external supply ,that's it controlling the bulbs isn't a big thing but Dimming is, However in Advance i will tell you about DMX systems or Velleman sort of Dimmer's which accept a vdc of about 0 to 10 VDC and control the Incadescent  or other sort of illumination stuff.