Ubuntu uses the Unity interface on top of Gnome 3 by default.
Whether you are using Unity or you have switched to gnome-shell, the launcher icons on your old gnome-panel have now been replaced by icons on a panel along the left hand side, known as the "launcher".
You can drag application icons onto there from within the dock (ie, searching for an application, then dragging the found icon onto the left panel). In addition, launchers you had on your panel back in Gnome 2 should have been migrated to Unity's new launcher if you had set them up manually.
Unfortunately, it is not possible to add application launcher icons to the top panel, nor is it possible to change the position or appearance of the launcher panel that appears on the left (or, at least, not much).
If you don't like the Unity interface, there are others. I would encourage you to get used to it, because it should be well-supported by Ubuntu people. However, 11.10 allows you to install the
gnome-session-fallback package, which gives you an alternative login option that allows you to have the old gnome-panel back.
These similar solutions may help