Often one wants to quickly generate an image from a small piece of TeX. (E.g. for inclusion in a question here.) What's the quickest way of doing it?
http://mathurl.com/ generates PNGs.
standalone package produces documents with a page size cropped to the text so the resulting pdf can be directly used as the image file in some circumstances. Search this site for
standalone and you'll see it used in many examples.
What I usually do for images for answers posted here (on windows) is I just run the example and preview in acrobat or xpdf or whatever and then use the print screen key and paste it into paint or some other editor and manually crop. That way I can crop to the part that is relevant to the answer rather than the full text of lipsum blah blahh that often gets used in examples.