www.wordtracker.com will give results for certain search engines. However, the figures you end up with are to be taken acording to their relative, rather than absolute values.

Meaning that if you are looking at two similar terms, and one shows as having 1000 searches, and the other as 10, those are not the actual traffic figures you should expect for ranking top for those search terms - but you should use those figures to note that the first search term has a lot more traffic.

In the paid version of wordtracker, you get the opportunity to do a KEI analysis of your targeted search terms - meaning, you get to see the level of competition for each search term. These are elements you can take into account for your titles, tags, and headings, and your battery of anchor text into the site pages.

Alright, Thanks!

http://inventory.overture.com/d/sear...ry/suggestion/

this cross compares overture and word tracker
http://www.digitalpoint.com/tools/suggestion/

and google search suggest uses search volume to help organize results
http://www.google.com/webhp?complete=1&hl=en

another option is to set up a test campaign and bid enough and use enough budget to ensure your ad will constantly show on said search results.

many keyword siggestion tools have artificially inflated search volumes due to bid checkers and traffic from other bots.