Gmail added yet another Labs feature, this time related to searching. If you enable "Search Autocomplete", Gmail will try to finish your query using names and email addresses from your contact list, built-in Gmail sections like "starred messages" and more advanced searches like "has photos" or "unread messages".
The new feature is especially useful if your search includes advanced operators like to: or from: because it's easier to enter the sender or the recipient.
Since Gmail doesn't show in the list of suggestions previous queries or common patterns from your messages, the feature has a limited use. You could get similar suggestions by typing names in the Gmail chat box and clicking on "View recent conversations".
Some other search-related Labs feature you should enable: Quick Links, which lets you bookmark Gmail pages, including frequent searches, Go to label, that autocompletes the name of a Gmail label, and Multiple Inboxes, which allows you to create a dashboard from different Gmail views.
Another quick way to view your contacts is to use the standalone page for Google Contacts available at google.com/contacts or google.com/contacts/a/domain.com. According to the Apps Update blog, "the new standalone contact manager allows you to manage your contacts within Google Apps without enabling Gmail". You can also use it with a regular Google account that doesn't include access to Gmail.