From MacYourself.com:
Most Dashboard widgets are useless pieces of crap. With that said, a good widget can be both fun and useful.
1.) iStat Pro
The ultimate widget to get an overview of everything that’s going on
with your Mac. At a glance you can check your CPU & RAM usage,
available hard drive space, network status & speeds, internal
temperatures, fan speed, battery levels, current processes, and more —
all with a great, elegantly designed interface.
2.) Amazon Album Art
iTunes automatically downloads album cover art for your music, but only
if you have an iTunes account and if they sell the music in your
library. If a song or album isn’t for sale in iTunes, no cover art for
you. This widget will quickly get album cover art from Amazon’s large
database for the currently selected songs in iTunes.
3.) Harmonic
Harmonic makes it extremely easy to get lyrics to your favorite songs.
All you need to do is play a song in iTunes, launch Dashboard, and the
lyrics will automatically display and copy right into iTunes. Lesser
known songs lyrics may not be available, but for the vast majority of
popular music it works great.
4.) xCuts
Remembering all the keyboard shortcuts Mac OS X has to offer is just
about impossible. When you need a good reference for shortcuts, the
xCuts widget will probably have what you’re looking for — right on your
Dashboard. You can even view by category and search the database.
5.) QwikConvert
Apple bundles a widget called Unit Converter with the Mac operating
system, but it’s a bit clunky and slow to work with. QwikConvert,
however, is incredibly fast and offers a ton of conversions that update
as you type. It doesn’t get much better than that.
6.) Asteroid Run 2
I don’t normally like games on my Dashboard because they suck up system
resources and fill valuable screen real estate. Asteroid Run 2 has me
hooked for some reason, though. It’s a fun little time-waster where you
navigate your spaceship through an obstacle course of asteroids to pass
through a series of loops before time runs out. It’s fairly challenging
and has decent graphics, so it’s definitely worth a try.
7.) Time Machine Buddy
Time Machine is an excellent feature introduced in Mac OS X 10.5
Leopard, but it doesn’t give users much feedback in terms of what’s
going on behind the scenes. For most people, that’s exactly what they
want. For others like me, a little more information is good to have.
The Time Machine Buddy widget will display the system logs generated by
each backup, whether they are in progress or already completed.
8.) Recently Added Widgets
If you’re always looking to make new additions to your Dashboard, this
is the perfect widget for you. It keeps you updated on the latest
widgets by grabbing the feed from Apple’s website to display the 20
most recently posted Dashboard widgets.
9.) iPassword
For some security freaks, a simple word-based password is the
equivalent of a technology sin. They can be easily cracked, which
leaves your online accounts open to hackers. The iPassword widget helps
to alleviate this risk by randomly generating stings of text and
numbers (at a character length of your choice), which you can use as
passwords when you sign up for new accounts on the web.
10.) Apple Retail Store Event Widget
Some people may not be aware that Apple Stores regularly hold free
events and workshops to teach visitors how to perform certain tasks on
a Mac, like creating a home video in iMovie or a song in Garageband.
This widget provides a list of upcoming events at your local Apple
Store so you know when to stop by for a presentation that interests you.
11.) gMap
Get Google Maps on your Dashboard with this lightweight, easy to use
widget. You can zoom in & out, use a variety of views (map,
satellite, and hybrid), and even set your home address as a reference
point. Sorry, no turn-by-turn directions though.
12.) UpcomingBirthdays
Forgetting birthdays of friends and family is a big problem for a lot
of people. It’s not that you don’t care… you’re just so busy you don’t
even realize, right? Unfortunately, that excuse can only work so many
times. This helpful widget takes your contacts’ birthdays from Address
Book and displays them so you can easily see when there’s one on the
way.

