Arusha has a plethora of accommodations options, far too many to cover in detail -- rest assured that those listed below truly are the best available in each price category.
Capitalizing on tourist flow into the Northern Circuit, most Arusha lodges differentiate between a high and a low season; some even have a "green" season, which is a euphemism for the wet season (Apr and May) when tourist traffic is but a trickle. Generally, high season is from June to October and mid-December to February, low season is April to July and possibly November to mid-December, but do check with your hotel when booking.
With the exception of The Arusha Hotel and Onsea, which are both in Arusha itself, the top recommended options all lie east of town, between Arusha and Kilimanjaro International Airport. All lodgings listed below offer airport transfers for a fee; I'd utilize these.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.