Call from Skype with front speaker
I believe you should be able to switch between Loudspeaker and Earpiece like this in the screenshot at the bottom while in a call. On my Samsung Galaxy 3 running a custom 4.0.3 ROM, it's working fine.

But after searching on Skype Forums I found this - Speaker only on Android device

Looks like a lot of people are having the same issue from initial releases of Skype for Android. Devices and OS are different in each case, so there really is no solution for users other than to wait for a fix from Skype.

You should perhaps look for alternative apps like these-


Fring (Fring Google Play)
SIP  (SIP for Android)
GTalk for Android app. (Supports Video/VoIP from Android 2.3 onwards). See here - xda-develoeprs GTalk w/Video &amp; Voice for 2.3.3 roms