This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
In case restarting the eclipse does not work try this :
After you have placed the com.sysdeo.eclipse.tomcat in the eclipse plugin folder, just go to the directory where you have installed eclipse from the command prompt and then launch eclipse once using this option : -clean
On the command prompt give -clean
i.e C>eclipse>eclipse.exe -clean
and that will get you the tomcat in the preference.