Other
Edinburgh: Natural Logarithm Function
Good detailed site explaining the natural logarithm. The site has links to related topics.
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Different Bases
Find a quick, concise explanation of how different bases work. A specific example is given for expressing numbers in base 3 and clearly explained.
Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Different Bases
Ten problems cover the topic of converting a variety of number to various bases. They are given with each step to the solution cleverly revealed one at a time. You can work each step of the problem then click the "View Solution" button...
University of Cambridge
University of Cambridge: Nrich: Back to the Planet of Vuv
You will probably need to make a list to solve the challenge at this one page website.