Abstract: During the final stages of AGB evolution, single red giant stars pulsate and lose large amounts of mass, enriching the interstellar medium in elements such as C, N and s-process elements. In this talk I will discuss the variability of AGB stars, including close binaries and the mysterious sequence-D stars which have so far defied explanation. I will also discuss Spitzer Space Telescope measurements of mass loss rates for AGB stars in the Magellanic Clouds. Such measurements offer the prospect of determining accurate empirical mass loss laws for use in stellar evolution and galactic mucleosynthesis calculations. Finally, I will discuss some recent observations of AGB stars with large nitrogen enhancements resulting from hot-bottom burning: these stars are thought to be one of the major sources of N in the universe.