Skype way too quiet. How to get louder Skype audio output on my MacBook Pro?

My girlfriend and I are getting really irritated with how quiet Skype is on my new MacBook Pro. Even with the volume turned up to the max, I can still barely hear her even with my air conditioning and fan off.

At first, I thought about buying a pair of speakers, but even the small USB ones would be irritating to have to have around all the time. Then I thought of buying a new sound card, but then I realized that iTunes with the preamp in the equalizer set to 12 is actually more than loud enough.

Is there a way that I could connect to that and make Skype that loud? Or is there any other way to make it louder?

On a smaller note, I've been having the same issue with movies played in Google Chrome.

Try the Boom system-wide volume booster tool. While it's not free, it is cheap: $6.99. See reviews here, here, and here. Below is the description from the product page, and a screenshot:

Boom is a simple volume booster and system-wide equalizer that lets you boost the volume of your Mac and your music files.

Using Boom is simple. You know the ways to change the volume of your Mac. Boom provides the same easy access to boost sound.

From the videos on YouTube, Hulu, your favorite music playing on iTunes, to voice applications like Skype, iChat and your favorite Games, Boom can boost them all. [...]

(emphasis above is mine)

I use Boom on my own MacBook Air and it does a reasonable job of increasing the internal speaker volume beyond what I was getting with the built-in volume controls at maximum. The graphic equalizer is an added bonus, letting me tweak the sound I get from these tiny speakers so it sounds a bit better for music.

Did you check the settings in the app "Audio MIDI Setup"? It's in /Applications/Utilities. Sometimes the settings there can get out of whack.