I installed skype from the RPM, but it does not work.

ldd shows that is is missing several dependencies:
[dan@dt-dan linux-2.6.30.x86_64]$ ldd /usr/bin/skype
linux-gate.so.1 => (0xf7f06000)
libasound.so.2 => not found
libXv.so.1 => not found
libXss.so.1 => not found
librt.so.1 => /lib/librt.so.1 (0xf7edd000)
libQtDBus.so.4 => not found
libQtGui.so.4 => not found
libQtNetwork.so.4 => not found
libQtCore.so.4 => not found
libpthread.so.0 => /lib/libpthread.so.0 (0xf7ec1000)
libstdc++.so.6 => not found
libm.so.6 => /lib/libm.so.6 (0xf7e98000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xf7e6d000)
libc.so.6 => /lib/libc.so.6 (0x00a24000)
libdl.so.2 => /lib/libdl.so.2 (0xf7e68000)
/lib/ld-linux.so.2 (0x00a00000)
libX11.so.6 => not found
libXext.so.6 => not found

What do I need to tell yum to install so that it'll work?

Enable the Skype yum repo (which Skype itself won't bother to document or even mention the existence of).

http://fedorasolved.org/multimedia-solutio...stalling-skype/

Then install with "yum install skype" which will take care of all dependencies.