I hope this is an easy / possible thing to-do:

I just setup the new Mbox 2 Mini with Pro Tools LE 7.1.1 on a MacBook Pro. I am able to record guitar to a track in Pro Tools, monitor it with headphones pllugged into the Mbox, and bounce the recording out to a .WAV file.

What I can't seem to figure out, however, is how to just listen to the playback in Pro Tools through computer speakers? I understand that this isn't the optimal listening environment by any means, but for just quick and dirty recordings and experimentation, it would be nice not to have to pull on the headphones while I'm also strapped into a guitar and everything at the same time.

I hope this is some output bus routing option or something like that?
I use ProTools LE and standard version at my school's recording studio, and neither of them playback through the computer speakers. For the Mbox, we either attach the headphones to it, or connect it to a speaker system. Not sure why it shouldn't come out of computer speakers tho.
Ibanez Xiphos XPT700
Laney VH100R
Epi Les Paul (SH-1 '59 neck, SH-11 custom custom bridge)
See this is the exact reason why people don't like Pro Tools in some cases because you have to use Digidesign hardware to do everything. As far as I know theres no way to get Pro Tools to play out of your computer speakers, and why you would on laptop speakers is beyond me?
yeah you cant do it, it routes all audio through the interface, and if you disconnect the interface protools will lock up. This is one of the many reasons why protools is lame.
make Industrial and/or experimental electronic music? Join my group!

Hmm, thanks for the info - I'm learning it because it's used at my work too, so it sort of kills 2 birds with 1 stone and all that...

Well, I have a Mackie 1202-VLZ Pro (the old one, not the new VLZ3) coming in the mail in a couple weeks, so I suppose I'll have to expand my physical desk space where all my guitars and computer are anyway, and start thinking about cheap monitors - I'll probably just start with those cheap $100 M-Audio ones for now, and then if all this ever turns into something bigger, I'll upgrade to something good.
this has nothing to do with pro tools. this applies to all audio interfaces. if you don't want to use your headphones for playback then just hook up studio monitors to the mon out.
All the audio going in and out of protools is through your mbox.
if you were to plug your monitors into your little headphone jack or somewhere on the mbox it would work.
Actually, the problem is with laptop speakers. If there was cable that you could plug into those speakers, you could send the signal out of your Mbox and into the laptop speaker amplifier and then onto the speakers.

Since there is no analog input on any laptop I've ever seen, you are out of luck.

In the end, a speakers in your laptop are basically the same thing as the speakers on stands (sound drastically different) but the hookup would be the same.

If you wanted to rip apart your laptop and get out a soldiering iron you may be able tap into your laptop's audio, but I would NOT recommend this.