The Compaq Presario 3000, 6000, and HP dv6000 using the nVidia MCP51 chipset all seem to have similar issues. My answer is "specific" to FC6, but you may be able to do the same things to get it fixed:
Pre 1.0.13 (i.e. 1.0.12): Does not work. You get speaker, but no headphone or mic.
1.0.13: Adding the "disable_msi=1" line to your /etc/modprobe.conf file gives you separate controls for onboard vs. jacks. However, this will work. You'll just have to turn your speakers off and your headphones on in the mixer. See my post here as to how I got this working: http://www.linuxquestions.org/questi...d.php?t=498344
1.0.14(rc2): Speakers work. Plugging in Headphone works (mutes the onboard speakers too). However, "muting" the speakers doesn't work (works only when headphones are plugged in) and the microphone doesn't work at all.
Given a different Distro, 1.0.13 may be your best bet. However, I'm stuck as Fedora has not released kmdl files for 1.0.13 with the latest kernels. I'm currently stuck being unable to upgrade my kernel because the latest alsa is not working.
Note, the afore mentioned thread was getting my headphones to work under 1.0.13. I am now on this thread trying to solve my 1.0.14/upgrade woes: