Where can I find Drosophila gene and genome information?

The FlyBase database is considered by many the 'go-to' resource for Drosophila melanogaster gene and genome information.
Additional resources include the following, many of which get their underlying fly gene and/or genome information from FlyBase.

FlyMine (good for batch searches with a list of genes)
Gene2Function (good for viewing an overview of gene information for a fly gene as well as for orthologs in other species)
DIOPT (good for finding orthologs of one or more gene among nine species, including humans and flies, for one or more genes)
Manchester Fly Facility 'fly links' and FlyBase External Resources, as well as the Information Resources page on this site (including the "online resources" and "online databases" categories), provide links to many additional and specialized databases.