Google has just made a change to its Keyword Research Tool to show the corresponding search volume for each keyword, meaning that Google now shows numbers instead of the usual shaded bars. This development by Google should receive a very warm welcome as it would help many keyword researchers in their tasks significantly.
This can also be considered as a replacement for the Overture (Yahoo) keyword tool which is by now already unavailable. Just make sure that you pay attention to the proper keyword match types for the given numbers.
A post in the Google Blog describes “Now, when you use the Keyword Tool to search for relevant keywords to include in your keyword list, you’ll be able to see the approximate number of search queries matching your keywords that were performed on Google and the search network.”