If you have the 32 bit version of Outlook, there's a simple way to import .eml files. Dragging and dropping them into a folder should successfully import the files with the metadata saved intact (the email addresses from the recipient field in the .emil file should be shown in the 'To' field in Outlook and so on.)
If this is not successful you can try importing the .eml files into Windows Live Mail, and exporting them to a .pst archive file from there.
If you are running the 64 bit version of Outlook neither of these techniques will work. You will be able to drag and drop .eml files into an Outlook folder, but the metadata will not be imported correctly. Instead of the correct author name, you will get the name of your Outlook profile; instead of the correct date sent, you'll get the current date and time.
Mail Passport Lite provides a solution to this problem. This application will import multiple .eml files and save them together in a single .pst archive file.
Open Mail Passport by clicking on the shortcut saved to your desktop. Simply browse to the folder containing the .eml files you need to process. You'll be prompted to select a location to save the new .pst file to.
When the .pst archive is opened in Outlook the metadata information will be displayed correctly.
The trial version of this application will only process 10 .eml files at a time. A license costs $99. Mail Passport can also process mbox archive files (used by Eudora and Mozilla's Thunderbird email application.