Links
Links to some random topics which I found interesting over the time.
A proof of Stirling's formula which does not use Gamma function
A series of Mathematical pamphlets started in 1963 by TIFR, Bombay has some excellent self-contained exposition to different subjects. Here is the link to get all of them in the series. http://www.math.tifr.res.in/~publ/pamphlets/index.html
Some Advice for Young Mathematicians (Editorial of the Notices of the American Mathematical Society, VOLUME 45, NUMBER 11)