Working with relays

I got a relay that I want to use with my arduino, but I wanted to verify some things before I try so I don't end up with a dead pin. All of the specs on my relay can be found here: http://htyp.org/275-0240_Radio_Shack_5-volt_relay

It says it has a nominal current of 89.3mA. I am using an arduino UNO which says it can supply up to 50mA per 3.3V pin. How can I manage to make it work? Will I need to supply power from the 5V pin on the arduino somehow? Can I run my relay from 3.3V? How can I deal with the current supplied and the current draw from the coil?

I'm totally clueless about the subject. I've tried looking around for a while, but I can't seem to find any straightforward answers that I'm capable of understanding. Thanks for any help!

Arduino Uno is rated at 40mA absolute maximum per output pin. So you'll need a transistor to drive the relay. See http://arduino.cc/playground/uploads/Learning/solenoid_driver.pdf for a suitable circuit; but for "solenoid" read "relay", use a small NPN transistor such as BC337 instead of the TIP102 shown, and the diode could be a smaller 1n4148 instead of the 1n4004.

Anyone new to this thread who doesn’t know about The Diode:

Read…

http://www.arunet.co.uk/tkboyd/ec/ec1relay.htm

… before you again apply power to a circuit with a relay, if you don’t have a diode across the relay coil.

Same considerations apply if you are controlling anything with a coil… motors, solenoids, electromagnets, etc.

Hi, schematic of how this is often done is here: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=181

DISCLAIMER: Mentioned stuff from my own shop...

Just to add some video to what has been stated, here are a couple short vids(of scope captures) of why that diode is needed.
http://www.youtube.com/playlist?list=PL1D237661606536A0 the second video clearly shows the voltage spike, as the relay is switched on and off.