Some useful links
Flybase: the world's premier database of Drosophila genes and genomes, online since 1994, with links to many Drosophila-focused web resources.
Alliance of Genome Resources: explore and compare genes in yeast, C. elegans, Drosophila, zebrafish, mouse, rat, and human.
Online Mendelian Inheritance in Man (OMIM): explore human genes and their links to genetic disease.