I've had my Nexus One for about a week and a half, and here are my favorite apps so far:
1. Touiteur From the creator of Beautiful Widgets, and this is definitely one beautiful Twitter app! It's also really innovative in the way it handles links, new tweets, etc. It's unlike any other twitter app I've seen. There are just a few things missing that I would want in a twitter app, but all in all, I think it's amazing.
2. Chomp SMS I like this better than HandCent. It's really just personal preference - I think they're both great, and better than the stock SMS app.
3. Beautiful Widgets I wish that I could show you a picture of my homescreen - I absolutely love it. My beautiful widgets Home widget is so pretty - I use the smaller home with a pink skin. And I can believe how long it took me to realize that if I touched the weather on the widget, it took me to a beautifully animated weather page. If I touched the calendar, it takes me to my calendar. If I touch the time, it takes me to the alarm clock. I was amazed, and so is everyone I show it to! (Most of you probably already knew it did that, but for me, it was truly a "Wow, I REALLY love Android" moment!)
4. Evernote I had this on my iphone and loved it, and I'm so glad it's on Android, too. I think it's actually set up better on Android than it is on the iphone - it's so easy to use, and I love how it backs up. Definitely my favorite note app.
5. Pure Calendar - I love the widget. And I love the fact that I can color code it, just like the actual google calendar. It's so easy to just glance at the widget and see who in my family has something coming up.
Honorable Mention:
1.Tweetcaster. I had this before Touiteur, and I think it's amazing too. It also keep adding new features, and updates on a regular basis. Handmark is doing a great job with this app.
2. Advanced Task Killer - I have it set to kill apps automatically every thirty minutes, and I also have the widget that I use periodically as well. I don't know about other people, but I have noticed a HUGE difference in my battery life because of this. Because of the scheduled task killer alone, this app is worth the money.
3.iReader - I looove reading on my phone. I don't think the size is too small, and I can just drop the book onto my SD card and there it is!