If you want to share your Outlook Contacts with only a few colleagues change to Contacts and then click the blue hyperlink in the Navigation pane that says Share My Contacts. Click the Add button, you will be taken to the Global Address List. Find the name/s of the person you wish to share with and click Add and then OK. The permission dialog box appears. Very carefully choose the permission you wish to give to the person you are sharing with and then choose OK again.

Sharing your contacts with your colleagues using this method means that they will each have to choose Open Shared Contacts when they are using Outlook to see your Contacts folder.

To make your Contacts into a public folder it is a two step process; first you have to copy the folder to public folders and then you have to give your colleagues permission to view/work in the folder.

In Outlook, change to the folder list and right-click the Contacts folder you wish to copy to public folders and choose Copy Contacts. The Copy Folder dialog box appears, choose Public Folders and find the location you want for your folder and choose OK.

To give permission to your colleagues to view the public folder, right-click the public folder and choose Permissions, choose Default in the name box and then choose Permissions and give everyone the permission level you want them to have. You will probably have to ask the system administrator to do this for you.