Use the package preview to generate .pdf files containing single pictures. Works particularly well with tikz. Use the following wrapper latex code, then run pdflatex on it.
\documentclass{article}
\usepackage{tikz}
\usepackage[active,pdftex,tightpage]{preview}
\PreviewEnvironment[{[]}]{tikzpicture}
\begin{document}
\begin{tikzpicture}[options]
...
\end{tikzpicture}
\end{document}Alternatively, you might use the standalone package to spit, e.g., multiple individual .png files
\documentclass[preview,multi,margin=2pt,convert={density=108}]{standalone}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\begin{document}
\begin{preview}
This is an example \LaTeX\ output.
\end{preview}
\begin{preview}
This is another with a formula: $e = mc^2$.
\end{preview}
\end{document}
