-help you obtain a list of words you usually misspell
-give you practice in note taking (FCE Listening Paper, part 2)
-foster thinking in the new language. Every learner's dream, isn't it?
Now, none of these benefits will happen unless you are motivated to practice dictation. If you choose how to practice it and try to vary the exercises, you'll focus more on its benefits rather than getting bored in a few minutes.
Here is a choice of websites to browse.
This site gives you three options of practice: jotting down the first letter of a word only, the whole word or a fill in the blanks with a bit of context to help you.
How can this practice help me develop listening skills?
Many students complain that listening is one of the most difficult parts of the test. Indeed, English has an isochronous rhythm that languages like Spanish do not share. Dictation can help you at the level of the sentence, the words, the division of a chunk of speech into sensible units.
For the FCE level, however, all of that is taken for granted. You will be asked to make assumptions, establish connections and not simply recognizing sounds and words. So, if listening is your stumbling block, why not get some dictation practice to help you break such a big task into manageable portions?