From Benito van der Zander:
TeXstudio is an integrated environment for writing LaTeX documents. Our goal is to make writing LaTeX as easy and comfortable as possible. Therefore TeXstudio has numerous features like syntax-highlighting, integrated viewer, reference checking and various assistants. All LaTeX tools can be called from TeXstudio with just one key press and you can add your own command line options, LaTeX tags and 1102 mathematical symbols you can easily select and add to your text, LaTeX errors are displayed in a Log panel and highlighted within the tex file, and scripting to control TeXstudio with user-written scripts.