You can now enter any category that you feel is best for your company in the category section of your Google Local Business Center listing. In the past, you had to select a specific category that was in Google's database. Now, if the business category is not listed in the database, no worries - you can still enter it.
For example, "web software" is not an available Google Business Local category. But I added it below and clicked "next" with no problem.
I discovered this new feature via a Google Maps Guide post at Google Groups, where Google Maps Guide Jen said:
Up until a few weeks ago it was true that we couldn't create new categories.
However, thanks to your many request, and to our Local Business Center team, you can now enter free form categories for your business in your Local Business Center account.
I believe the category you set in the Google Local Business Center is extremely important in ranking well for local specific results in Google Local and Google Web Search, when universal search kicks in.
Forum discussion at Google Groups.