For my project I have an arduino Uno connected to my robot. I need to control it wirelessly. I have thought of using a bluetooth module , but I need a larger range. Then I thought of using an RF-module like the Xbees and the 2.4 Ghz nRF24L01. However I can't use the Xbees due to budget issues. As for the nRF24L01- I understand that using the trasmitter and receiver modules I can transmit information between 2 arduinos- however I need to transmit from my computer to my remote arduino. I want to achieve this without using a second arduino at the transmitting (computer) end. Is there a way to achieve this?
How about using wifi? The esp8266 costs as low as 3$ and has good range. here's a quick tutorial What you'll need to do is send a command to the esp8266 and in turn it'll communicate with the arduino via Serial (or Software Serial) and tell it what to do.
It is also not very cheap, but you can easy use wifi shield. The one I sent you is from arduino, but there are chinese analogs which are cheaper. You can use them either to connect your arduino to computer or to connect it to the other devices. Have fun!