Ok, so i am new to all this.
I am a Uni student doing Electronics and Communications Engineering and when i spotted that Ubuntu 7.1 came out i thought i would give Linux a try, thought its "open source"ness might come in handy with my programming course. Well i have only been running it for a little under 48 hours but i have to say i am very impressed.
Anyway, onto the question.
I am using an Acer Aspire 5630 and i can't get my microphone to work. I was using Skype and it had several different possible options under the "Sound In" section so i did a test call with all the options but the mic worked with none of them. Can anyone help? Is there anything i can do to extract more information so you can offer a better solution?

What does: cat /proc/asound/cards

give please?

Have you run alsamixer or kmix to see whether the mic gain is turned up on the sliders?

Also, do your speakers work?

0 [Intel ]: HDA-Intel - HDA Intel
HDA Intel at 0xd0340000 irq 22

The speakers work yeah.

OK, so did you try alsamixer and look at slider positions?

Well, it seems that the volumes for the microphone were turned right down. I turned them up but i still have no voice in a skype call.

Do you have different mic sources? Did you run kmix or alsamix? Make sure you try every combination of mics both on kmix/alsamix and Skype. One other possibility, I once had a laptop that had a pot somewhere on the side that changed the gain! It seems unlikely that the drivers work for the speakers and not the mic.

These steps may help (they did it for me):

http://ubuntuforums.org/showthread.php?t=586821