Change pitch on internal microphone.

Generally you record a standard waveform and then alter it to have a higher pitch, as opposed to altering the input itself. You can do this with GarageBand, if you ahve it installed. Just start a new voice project then select the input track and click the "Real Instrument" section of the sidebar, followed by clicking the "Edit" tab. In here click one of the empty rectangles and add the "AUPitch" filter. Then click the icon for the filter and you can change the pitch and other features that the filter offers. In addition to a basic pitch option, you can use others like the "Speech Enhancer", and "Vocal Transformer" filters to adjust vocals.

That would depend on the capabilities of the conferencing program you're using. I don't believe either Audacity or Garageband will pipe its output to other programs, so you would have to have a special Web conferencing program that supports pitch bending features in order to do it. Alternatively you could use two computers and send the output of one to the input of the other (though be careful because the computer's analog output is powered, and can overload the input of another system unless you have the volume very low.

Audacity (free) will also let you change pitch of recordings.

BTW the "Vocal Transformer" filter will allow you to do things like change from male-sounding voice to female and vice versa, which may be what you're looking for here.