First point. All applications that were written on 1.x (1.1.4 and lower) will not run on 2.0 iPhone. This is a common misconception. People think that they just need to add the source to installer. Wrong. It is not a problem of adding  a source. The apps simply do not work. That is why they are not available to you on 2.0.

1) All 1.1.x apps must be rewritten to run on 2.0 and will not work.
2) All sources you need come with Cydia by default on 2.0. You do not need to track down sources.
3) You cannot add installer sources to Cydia. They are different and incompatible.
4) You cannot add installer 3 sources to installer 4.
5) You should be using Cydia on 2.0 not installer 4. Installer has about 1/10th the packages that are in Cydia. On 1.1.x, installer was the app to use. On 2.0 this has changed. You should use Cydia now. At the time of this writing, there are some 900 packages in Cydia and only about 90 in installer. The packages in installer are also in Cydia. Your key packages are not in installer.
6) If you get “cannot decode package” you have added an installer 3 source to installer 4. Delete it.
7) If you do not have Cydia, you must rerun quickpwn.

So, you updated to 2.0 and you’re now missing your favorite app or game? It’s not a problem of adding the source. It probably has not been rewritten for 2.0 OS. As a side note, the combination of Cydia + Appstore gives you so much more than you ever had available on 1.1.4 anyways.