Yes, you can accomplish this using "Categories." From an outlook calendar entry, click Categorize (from the ribbon or by right clicking an entry in the calendar view). You'll see various colors to choose from. Rather than using the color name, you can rename the categories by clicking All Categories. You can use up to 25 colors.
These categories will apply to Mail and Contacts as well, so you may want to create additional categories for these Outlook items. If you wish to apply categories to mail messages or Contacts, just right click and select the category (or select the 4-color Categorize icon in the ribbon). You can then sort on categories in your mail. In addition, you can set up quick click (default) categories for your most frequently used topic so that all you need to do is click the category box (next to the Flag) in your message view.
Another shortcut using Outlook 2010 and 2007 is to create a calendar entry from a message by dragging the message to the calendar on the to do bar. (show the To do bar from the View tab on the ribbon).
Learn more shortcuts and share your own tips at Wednesday's Calendar Tips mini-session, March 6 from 2 to 3 p.m. in the ITS training room, 8011 Wittson Hall. Register and learn more about March/April offerings.