Just as some examples...
High GI (70 or over)
Potatoes - baked or boiled
French fries
Many breakfast cereals (wheat flakes, cornflakes, rice bubbles)
White bread
English muffins
Bagels
Crispbreads
Rice crackers
Most white rices, especially Jasmine rice & Rissotto rice
Lollies - ie. jelly beans
Medium GI ((56-69)
Wheat biscuits (Wheetbix-type breakfast cereals)
Basmati and Doongara Rice
Wholemeal & Rye breads
Most biscuits and cakes
Crumpets
Sugar
Soft drinks
Some fruits (apricot, pineapple, rockmelon, sultanas)
New or canned potatoes
Low GI (55 or less)
Milk
Yogurt
Low-fat icecream
Grain breads
Pasta - all kinds
Porridge/Oats
Barley
Most fruits (apples, oranges, peaches, pears)
Sweet potato, peas
Lentils and other legumes
Baked beans
Nuts
Many types of noodles (not rice noodles).
As you can see, GI can be pretty confusing! I mean, how are canned potatoes medium GI but baked ones high GI? It's all a bit of a science, so that's why you've got to read up a bit. There's lots of info on the net, this site even gives you a GI food database!
http://ziag4.mmb.usyd.edu.au/mainV4a.htm
But it's worthwhile looking into, because with a few "tweaks" to your diet - ie. eating pasta rather than rice, whole grain bread rather than white - you can stay fuller longer and avoid blood sugar dips and spikes.