I find that the transition from local business to national business pubs is very straightforward -- my husband did it in a few months.
Here's my advice:
• Hire a cheap college student to set up a web site for you. Feel free to have him steal mine. A low-cost way of doing it is to take the free webspace that you get with your email account (which has a nasty-looking URL, I'm sure), pay $10 bucks to register a domain with mydomains.com, and have the new domain forwarded to your free but ugly one (but visitors will only see the nice clear URL you registered.).
• Get a list of pubs who might be interested in business or technology writers (go to Google and type in -- "managing editor" "business editor" -- or "business editor" "technology editor" -- to get newspaper and magazine mastheads. I've done that, and am currently working with a database of about 500 editors at target pubs (and I've hired my brother to keep the database current and expand on it) because I use it a lot for marketing and it's a pain to do it from scratch each time you want to send out some queries.
• Pick a general story topic that could be of interest to many different kinds of pubs -- for example, is it time to upgrade to Windows XP? All the bugs are now discovered, support for Windows 2000 and Win 98 is about to expire soon, there are patches for major vulnerabilities, drivers are in place, etc... Any business (or consumer!) publication could use a story like this -- if they haven't run one already. For example, you might want to target local newspapers, write basically the same story for each one, but quote a local business owner (easy enough to find -- call the local chamber) instead of the one you had.
• Write a query letter titled "freelancer introduction", say you're an experienced business and technology writer in the first paragraph, mention Windows as a particular area of expertise, give links to a couple of clips on the topic, a link to your website, and suggest a possible story topic. (I find that I've had a good response to this approach, but editors usually assign me something different from what I suggested!)
• Now send this same letter to a whole bunch of different editors. Except in the story topic, you would customize it for their publication -- when hotel managers are planning to upgrade, or
• If you come across a particularly interesting story topic, don't hesitate to pitch it to national publications the same way -- start with trades, they pay well and are easy to break into to ($.50 to $2.25 a word) as well as computer mags like Computerworld, eWeek, InfoWorld, Business 2.0.