I was using pixie for picking colour and pixel ruler for measuring. Now i got a free application which have both this facilities and many more.

• Screen capture
• Full Screen
• Active Window
• Specific region
• Free hand
• Image Editor
• Colour Picker
• Pixel Ruler
• Screen Protractor
• Cross Hair
• Screen White Board

You will find this application very handy. read more and download about PicPick. Installation exe size is just 1.2 MB and zipped size is just 865kb.