Influential tech blogger Michael Arrington announced the "Web 2.0 Companies I Couldn't Live Without" for 2007 today. The list of 15 web services – including Digg, Flickr, Gmail, Skype, Techmeme, Wordpress, and YouTube – is interesting as a collection in several ways.

My first thought is that while most of these services didn't exist two or three years ago, they really are indispensable to the daily life of many web users as 2007 dawns. And that's striking because it shows you what a flattening force technology (and "web 2.0" as its modern Internet equivalent) really is. I can look at the list and know that I use many of the same information-gathering and communications tools as "influential tech blogger Michael Arrington," for instance.

If e-mail was one of the Internet's earliest (and some might still argue only) "killer apps," I agree with Mr. Arrington that Gmail is just about its perfect web-based incarnation. The ability to tag messages (you can put label a message however you like and have it saved to multiple folders), instant refreshing (messages pop up without you having to do anything), and threaded messaging make it an essential everyday tool.

Two of the selections – Amie Street and Pandora – are music related. I've been intrigued by a service called eTunes of late, which has kind of an "early beta" look to it but is a really easy way to gather music online and then stream it at will.

While I think that Digg is probably the best current incarnation of the new breed of "social news" sites (though I think the future lies with hybrid models spearheaded by Netscape, a meshing of an editor- and user-controlled experience), I'm partial to Reddit because of its simplicity and the mere fact that it casts its net to a range of stories that I happen to find interesting. Reddit's innovation to allow users to vote stories "down" may actually be its worst feature as it encourages active news submitters to vote stories down. However, voting comments down, which Reddit employed before Digg added the feature, is great. Nothing's more satisfying than clicking a down arrow on someone you disagree with!

While Mr. Arrington uses NetNewsGator and NetVibes to read and organize RSS feeds, I'm partial to a combination of Bloglines and RSSFwd. NetVibes, part of the new breed of "web 2.0 start pages," is a great product but the prospect of staring at a bunch of boxes crammed with news headlines doesn't quite work for me in general. That said, I'm nearly awed by what a super-cool product yourminis is.

The other things that I use everyday include Basecamp, project management software put out by the 37 Signals folk, and AIM for instant messaging.

What's finally intriguing is that there is not one social networking product on Tech Crunch's (or my!) list. I wouldn't be surprised if this will change in the next year or two, as companies fall all over themselves developing more sophisticated social networks that cater to an older/more mature demographic and an ever wider array of specific interests and lifestyles.