There are a ton of services out there, but the following list are six things I wish all of my friends had. Why 6? I initially came up with 11, but 6 all fit a simple, helpful criteria.
1. Flickr - Photo sharing was made for social networking. How many years will we have to continue to send compressed digital photos via email? Not free, but affordable and an easily justifiable value.
2. Last.FM - A service that tracks the music you listen to and lets your friends follow that as well as makes suggestions of new music. You can even go online to remove your guilty pleasures if you don't want your friends to know about the 12 Air Supply songs you listened to at 9pm on a Saturday night. Free.
3. Twitter - Microblogging. My true wish is that all my friends would have blogs, but Twitter is easier to update regularly and easier to keep up. Lots of creativity lately in how it's being used. Why Twitter over Jaiku or Tumblog? Twitter is easy. Free.
4. Skype - How many times do I have to say voice IM before it sinks in how awesome Skype can be? Is the headset/microphone the obstacle to entry? (Yes, ReckenRoll, it's made for UK/US communications) It's free for Skype to Skype "calls," and you can upgrade to include Skype to phones for a very reasonable cost.
5. LinkedIn - I've already used it to hook a friend's workplace up with the opportunity to bid for some work. I like how it searches your contacts in Outlook and/or Gmail and lets you know who's on LinkedIn already, then gives you the option to add them (gmail saves anyone you've been in contact with as a contact, so people who I'm either not friends with or I don't want to give all my contact info to show up and can be omitted) rather than spamming everyone. Free.
6. Del.icio.us - It's a great tool for a workgroup who find themselves sending links via email. Using the Firefox plugin with some strategic tags makes sharing great links so much easier. If you're dependent on your favorites/bookmarks, you can also use Del.icio.us as a portable substitute. Free.
Of course, my endorsement of these 6 services means I'm a user of all 6. If you check them out and want to add me, let me know. If you have a service you wish I had, or wish your friends had, let me know and I'll give it a whirl. You know me not always an early adopter, but always either early or an adopter.