Can’t afford Photoshop? The open source GIMP has much of the same functionality and is completely free.
JR Screen Ruler will allow you to measure the size of anything on your screen in pixels. I find it very useful for tweaking web site designs.
20q.net will guess just about any object that you can think of by asking you 20 yes/no questions.
For internet and media utilities I recommend AnalogX. Their tools are all free and very high quality.
Need to know right when you get e-mail? {{link http://www.dectsoft.com/products.php Ease-E-Check}} Sits in your system tray and checks for new e-mail every two minutes and plays a notification when it finds new mail.