I want to do some comparisons of angle iron vs tube and their strengths, wondering if anyone knows of a good online calculator or chart.

For an open ended question like that, everything you need to know is in this book. It's a good read.

http://www.amazon.com/Statics-Mechanics-Materials-Integrated-Approach/dp/0471434469/ref=sr_1_2?ie=UTF8&s=books&qid=1252178595&sr=1-2

Mark's mechanical engineers' handbook.

Machinery handbook.

Both will have more info than you'll know what to do with and it will be more applied than the theoretical stuff one might find in a textbook.