Alright, so I'd like to use the following items for my project: a small 16x4 sparkfun LCD, an IR reciever, and two servos.. the only problem is I'm limited to 6 volts and need to be able to go a continuous 4m/s for about 45 seconds on one set of batteries. Will I be able to do this? Additionally, what's a reliable source for servos (that I can preferably get next day shipping on and get next day)?
Excuse any of my ignorance, I'm new to all of this 
i dont get what you mean about a continuois 4ms with batteries, but for my servos, ive noticed 6 volts is perfect, so if i were you, i'd get the radiosahck 4 AA holder with the switch... it's cheap, its reliable, and it lets 2 servos run with no shown difficulty or strain on the servos, even when both are running at the same time!
as for using all those items at once, i'm not sure, becuase i tried to use an h bridge and a servo together, and it messed eachother up, so i dont know if using all of those at the same timke will mess up one another...
but hey, try and see!
Is there any necessity for an H Driver considering I'm working with Servos?
By a continuous 4m/s i mean that the actual device itself will have to roll on its wheels (attached to servos) about 4m/s, so the servos have to rotate pretty fast (modded for continuity).
no, i was just stating that compatibility issues do arise sometimes when dealing with more then one thing. like lets say i had problems working with the servo library and an h-bridge at the same time, while you with your many different other things, like the lcd and display, may have other problems, like i don't know if the servo library will work the the lcd, it might not...
like i said, test..
Woops! I ordered two servos and realized that they can only pull 60rpm (which seems typical of servos now that I look at it). Anyone know where to find tires with a 4m circumference 
Is interfacing with an H Driver/one-two motors hard with an arduino? I can't find much information about it.
If you search for H bridge in the forum you will find it.
H bridges are primarily used for DC motors, not for servos.
To run to DC motors with both speed and direction control you would need 2 H bridge IC's
They are not very difficult to control with the Arduino
Or you could go for something like this :
I ordered a Tamiya single motor + gearbox from Pololu last night. I realized I didn't need an H Driver as I don't need directional control, only speed. Any suggestions in that regard?
You could use a couple of radio control Electronic Speed Controllers (ESC). They are relatively inexpensive and you can control the speed using one of the servo libraries. Although they take the same signal as a servo, they are designed to power an electric motor.
Some examples are here: bphobbies.com - bphobbies Resources and Information.
there are plenty of servos out there that are ok at 5v (4.8 - 6 actually)
http://www.servocity.com/html/hitec_servos.html
http://www.servocity.com/html/futaba_servos.html
Check out some specs here.... though I have to say bp is also a great vendor if yo are on the east coast.
What's the average RPM around hobby servos?
there are plenty of servos out there that are ok at 5v
The OP was hoping to use continuous rotation servos to drive the wheels but found that the rotation speed of even the fastest servos was not quick enough for his application. typical servos move at speeds slower than 60 degrees in .1 second (100 rpm)
I just read a but more carefully if you just need control of two dc motors(one direction) why not just use two tip120 ?
h-bridge tutorial
http://itp.nyu.edu/physcomp/Labs/DCMotorControl
tip120 tutorial
http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads
They are both pretty simple, I've done both... if you need only two motors in one direction I think the tip120s will work... then again you can do the same with an h-bridge, and have a reverse option on tap should you want it at a later date.