Generally you won't see much in benefits from a temp agency. You'll only get paid when you work. You can register with multiple agencies, that may help you find a job - plus you'll get a feeling for each individual agency. A lot of companies use temp agencies or consulting companies to find people to hire (temp to perm is how the position is usually described), but don't count on a temp position becoming permanent, sometimes they never get around to creating the in house position, or you are a fine fit as a temp, but they choose to go elsewhere to hire, or you decide you can do better elsewhere.
What kind of agency depends on what kind of work you are looking for - some specialize in accounting or IT, some in general office, some in manufacturing. Some are generalists or have divisions for different kinds of work. Temp agencies who place skilled workers are generally called "consulting" or "contracting" agencies. (I run one where our clients pay us $140 an hour for IT developers)
Be flexible and ready to work. Go into it with a good attitude.