Susan Winebrenner's Teaching Gifted Kids in the Regular Classroom is filled with practical activities and general information for working with gifted students in small groups or on an individual basis. The book also contains a list of other resources that are geared toward the classroom teacher.
A similar book for teachers is Teaching Gifted and Talented Learners in the Regular Classroom, edited by Robert Milgram.
A great general resource on the gifted is Barbara Clark's classic Growing Up Gifted. Clark's book does an excellent job of describing the gifted with particular attention to their developmental stages.
For curricular information seek out Joyce Van Tassel-Baska's Planning Effective Curriculum for Gifted Learners.
The journals Roeper Review, Gifted Child Quarterly, and Journal for the Education of the Gifted can provide additional valuable information. Your local (public or university) library may carry these journals.
Beyond readings, do check to see if your state department of education or district office has a gifted program specialist. That person may have additional materials or may offer in-service workshops for teachers of the gifted. Your state may also have a gifted education association composed of parents and teachers of the gifted. Such organizations often hold annual meetings where teachers present examples of lessons they have developed for use in their classrooms.
The National Association for Gifted Children (nagc.org) will hold its annual meeting in Cincinnati in early November. The NAGC convention is packed with excellent sessions for teachers and includes an exhibit area featuring the latest instructional resources. The Council for Exceptional Children (cec.sped.org) holds a similar meeting in the spring. The upcoming meeting will be in New York in early April.
Finally, don't overlook your colleagues at school. If there are other teachers of the gifted, talk to them about their experiences. They may be willing to share resources they have used over the years.