Which RPM provides a particular file or dependency

Here is how to find out which RPM file provides a particular dependency:
# yum whatprovides <filename>

For example:
# yum whatprovides libQtDBus.so.4 <enter>

This returns result as follows:
Loaded plugins: fastestmirror, langpacks, presto, refresh-packagekit
Loading mirror speeds from cached hostfile
* fedora: mirror.cse.iitk.ac.in
* rpmfusion-free: mirror.cse.iitk.ac.in
* rpmfusion-free-updates: mirror.cse.iitk.ac.in
* rpmfusion-nonfree: mirror.cse.iitk.ac.in
* rpmfusion-nonfree-updates: mirror.cse.iitk.ac.in
* updates: mirror.cse.iitk.ac.in
1:qt-4.7.2-8.fc15.i686 : Qt toolkit
Repo : fedora
Matched from:
Other : libQtDBus.so.4

Now you can give a command to install qt-4.7.2-8.fc15.i686 (note the bold rpm file returned above by the yum whatprovides command) using:
# yum install qt-4-7.2-8.fc15.i686 <enter>