A couple of weeks ago, I described how to sync contacts between Outlook, Gmail, and your iPhone. The program missing from this contacts mega-merge was Thunderbird (download for Windows | Mac), and for good reason. Mozilla's free e-mail program is not particularly contact-friendly.
The first time I attempted to use Mozilla Thunderbird's import function to bring my Gmail contacts into the client e-mail application, I was seriously disappointed with the results. Most of the contact information was squished into a single nondescript field for each record. The few fields that did make the conversion were incomplete. The entire process was pretty worthless, overall.
Then I found the free Zindus add-on for Thunderbird. The program brings a subset of contact fields from Google and Zimbra into Mozilla's free e-mail program. For Google, the fields imported include the contact's name, primary and secondary e-mail addresses, phone numbers, IM names, company, title, and notes. (I didn't test the program with Zimbra.)
After you download and install Zindus, a "Zindus" option is added to Thunderbird's Tools menu. Clicking it opens the Zindus Configuration Settings dialog box where you're presented with a handful of contact-sync options, including a Sync Now button.