Most hotels do operate in the more touristy regions of the country such as Amboseli, Nairobi, Samburu, Maasai Mara, Nakuru, Elementaita, Kilifi, Mombasa and Diani. Many of them that are in cities that have airports do operate shuttle services while some in hard to reach game parks and reserves have airstrips.
There are a number of other guesthouses that offer private rooms both with shared bathrooms and self-contained rooms for between KES1,000 and KES 4,000 per night. As long as you don't mind basic accommodations, there is no need to spend more than USD100 per night on a hotel or hostel. In less touristy areas, lodging can be found for as cheap as USD5 per night. Be wary of bed bugs, though - it may be advisable to purchase insect spray and bring along your own sheet if you plan to travel very cheaply.
More luxury oriented travellers will not be disappointed as there are a wide array of luxury hotels in the country. From traditional international brands like Kempinski, Fairmont, Radisson, Intercontinental and Hilton to smaller local, but just as good chains, such as Serena and Hemingways.
Homestays are increasingly gaining popularity. Part of the reason is that one is able to experience Kenyan culture in a deeper and more meaningful way. Most homes charge about USD20 per night inclusive of meals. Some may include laundry on that price.
People staying longer-term may rent accommodation; prices range from estate-agent 'international style' rentals at USD150+ pw, to privately arranged furnished apartments, from USD50-100 pw, to 'local' style accommodation, usually unfurnished, in a price range from KES5000-7000 per month with windows, water, electricity, down to KES 500 per month with no windows, no electricity, loud neighbours, mosquitoes, shared access to a tap. To arrange privately rented accommodation, you'll need to ask around - cab drivers, shopkeepers, market traders, could all save you the estate agents' fees.
One may also consult Airbnb while in Nairobi as there is a growing number of listings on the site, however do take all the necessary precautions as one would when using airbnb in any city around the world.