InDesign CS3 allows you to enter a "non-joiner" character in text by choosing Type > Insert Special Character > Other > Non-joiner. A non-joiner character is a character that has no width. Tim Cole explains the intended use for the non-joiner character here.
I've discovered another use for this character from a recent project. I had a list of items, to which I had applied bullets using the automatic bullet feature (Type > Bulleted & Numbered Lists > Apply Bullets). On one of the items, I needed to make the first word red. But this caused the automatic bullet to become red also, since automatic bullets inherit the formatting of the first character of the paragraph.
Creating a character style for the bullet would fix this, but that was overkill for this simple project. Instead, I inserted a non-joiner character at the beginning of the paragraph, selected the non-joiner, and made it black. Problem solved.
Since the non-joiner has no width, it is tricky to select. The best way is to position the cursor to the immediate right of the character, and then hold down the shift key while you hit the left-arrow cursor key.