The Iowa Department of Transportation, Office of Contracts has an option to receive automatic notices when pre-bid information becomes available. I have signed up for all the notifications and I can tell you it does give your inbox a work out. I particularly like the eligible bidders list that gets sent prior to the letting. This list is much more usable than the information posted on Bid Express.
To sign-up go to http://www.iowadot.gov/contracts/subscribe.html.