Firefox: Find Suggest is a free offering from Mozilla Labs that adds in search term suggestions to your in-text browser searches. Type in the first few letters of your search term and Find Suggest suggests words from the document that match.
Click on the image above for a closer look.
After installing Find Suggest the regular old CTRL+F search query looks the same as always. When you start typing a search term, however, you'll notice that suggested terms appear to the right of the query box — the highlighted words in the screenshot above. Clicking on the suggested word filled in the query box with your selection.
Find Suggest is a free extension and requires Firefox 4 or above.