Tough in this economy -- I know a lot of people who are cutting back on what they consider optional services, both individuals and companies. My own employer has cut back drastically on our office cleaning services (we empty our own office trash cans and vacuum our own offices nowadays).
What sort of benefits are you mentioning in your ads? If you're not getting good responses from them, maybe you're not hitting on the right "hot buttons" to motivate people.
Seems to the things people are still short of these days, even more than money, are time and energy. They're working extra hours to make up for laid-off colleagues or taking on second jobs to make ends meet.
Some kind of focus on how your services will allow people who are swamped with work to have a house into which they can be proud to invite company, and yet still spend as much of their precious time as possible with their families (instead of scrubbing the kitchen floor or whatever), that might resonate.
You could also try partnering with realtors (and advertising directly to homeowners) for a "detailing" service for those who are trying to sell their homes. The market's competitive, maybe a few dollars spent to have their home professionally deep-cleaned could make the difference between a quick sale and sitting on the MLS site for weeks/months. Direct to homeowners would be a bunch of one-offs, but by partnering with several realtors, you could get a steady stream of referrals.
Perhaps you could even find local home stagers and partner with them to deep-clean houses they're staging, or subcontract them to allow you to offer staging services as another option. (Or you could learn home staging and offer the service directly yourself.)
To make contact with realtors and stagers, you're probably best off visiting them personally -- maybe dropping off a bucket with some cleaning supplies and sponges/rags and a duster along with your business card and a personally-written letter introducing your services and mentioning the benefits (clean houses result in quicker sales for more money, for instance). Then follow up with a phone call to set an appointment to discuss in more detail. Maybe offer them a discount if they sign a contract committing to a certain period of time or a certain number of houses rather than going with one-offs.
For offices, if you haven't already, get creative with offering "a la carte" services -- let them pick and choose how often you come in and what exactly you do while you're there. Maybe even borrow an idea from restaurants, and have a menu of services they can choose from. You could have some fun designing the menu and running with the whole restaurant theme, even.
Make that customization a focus of your advertising to commercial accounts: how you can help them keep a presentable office/store/whatever that will give their customers a good impression, and do it by allowing them to customize your services to fit their needs and budget.