Which tools seem the most useful so far?

I'm waiting for an update to install so thought I'd do a post (it seems to let me write and update at the same time).
So reflecting back on what we've done so far (nearly at the end too!!)

Well the software loaded and its now a weekend later.
Its a hard one - which will be most useful - some things are obviously useful - rss, blogs, wikis, delicious - others not so obviously so.
Second Life is the most fun - but maybe not so immediately useful - and then things that I would have dismissed straight away such as Twitter - I have actually found quite good in a work sense (though it needs to some how automatically refresh).

I think most things have potential uses and maybe learning about all the things combined is what is most useful - it means as you are doing something in the future you can think - "I wonder what would happen if I tried to use a xxxxxx for that?"
And the more you keep learning and trying the new tools - the more familiar some of them are becoming - which means that sometimes you may in fact been using them without thinking about it at all.....