The increasing flow of tourists to Iceland requires more workers. To be hired for in-demand summer seasonal work (eg housekeeping and hospitality in hotels, guesthouses and restaurants) you must be from the EU/EEA. If you're after a professional job, Icelandic language skills may be a prerequisite (exceptions exist in the growing computer programming and gaming industries, and in tourism).
For non-EU/EEA nationals, things aren't so easy – you must have a work permit, which most commonly requires sponsorship from a local company. Full details are outlined on the Directorate of Immigration's site: www.utl.is.
One of the best places to start gathering information and contacts is the website of Vinnumálastofnun, the Icelandic Directorate of Labour (www.vinnumalastofnun.is). It provides information on work in Iceland, plus links to agencies that may be able to help.