I have quite a few of the following gadgets on my page, and have weeded through the masses to come up with the ten I think, are the most useful of them all.

This gives you up-to-the-minute news, breaking news, video, audio and feature stories, as well as entertainment, business, science, technology and health news. All of these are delivered straight to your page when you log on to the internet. If you use Digg, SU, Delicious and other social networking websites, this is most beneficial to you, as you won't have to go digging around for material to submit.
This gadget has 428,090 users, and has an overall rating of 4.5 out of a total of 5 points.

You get live weather sent to your page. All you have to do is edit it to show your local forecast. You can also include 3 other cities' forecasts of your choice. If you work away or travel a lot, this one would be extremely useful.
This gadget has 94,000 users, and an overall rating of 4 out of a total of 5 points.
This search module searches YouTube by tags, and delivers a more thorough experience of the site.
This gadget has 66,585 users, and an overall rating of 4.5 out of a total of 5 points.

This is said to be the most popular currency converter on iGoogle. It has the capacity to convert 180 currencies and commodities, and offers up-to-the minute foreign exchange rate calculations.
This gadget has 105,876 users, and an overall rating of 3 out of a total of 5 points.

This enables you to find places with Google Maps without having to leave your homepage.
This gadget has 1,896,215 users, and an overall rating of 4.5 out of a total of 5 points

This is vital for writers, as learning a new word every day enhances your writing beautifully. Some writers tend to use the same words regularly, which can cause their writing to become dull and boring. Word of the Day is one of the most useful iGoogle tools, because a large vocabulary gives your writing style lift, and an air of confidence. This gadget also includes synonyms and usage examples.
This gadget has 181,634 users and an overall rating of 3.5 out of a total of 5 points.

This fantastically useful iGoogle gadget helps you to keep your plans on track. The gadget allows you to add your tasks, highlight them in different colours, change their order on the list and strike-through or delete tasks that are done - everything you need to get things done! I also use it to remind me of ideas I've had for articles I want to write.
This gadget has 49,515 users and an overall rating of 3 out of a total of 5 points.

This is another super gadget for your homepage. It will search through Dictionary.com, Wordweb, Wiktionary, Cambridge or Etymologyonline.com, Google Maps, News, Images, Books, and Gadgets, and lets you customize it to your own needs and liking.
This gadget has 37,826 users, and an overall rating of 4 out of a total of 5 points.

A fine way to train your brain. Use this iGoogle gadget to spend less than a minute every day, to give your brain a bit of exercise. Do this before you start work daily, and it will help you to keep functioning to your full potential
This gadget has 8,696 users, and an overall rating of 4 out of a total of 5 points.
Get your fix of ‘how-to' each day when you sign in to your iGoogle homepage. This gives a vast amount of different how-tos, from which to choose. Who knows, you may find something you've always been hoping to learn.
This gadget has 135,867 users and an overall rating of 4.5 out of a total of 5 points.