Wizards of the Coast has announced its summer RPG releases, planned for release in the May through August period.  Its biggest releases for the summer, the 3.5 editions of the D&D Player's Handbook, DMG, and Monster Manual, were previously announced for July (see 'Wizards of the Coast Goes Beyond Third Edition').  Here's the rest of the line-up:

May

Unapproachable East, by Richard Baker, Matt Forbeck, and Sean K. Reynolds.  Unapproachable East is a Forgotten Realms accessory with descriptions of people, places, and unique cultural elements from the eastern region of the Forgotten Realms world.  Includes new spells, magic items, feats, character races, prestige classes, and monsters.

Urban Arcana Campaign Setting, by Bill Slavicsek, Jeff Grubb, Eric Cagle, And Dave Noonan. 

Urban Arcana is a d20 Modern campaign, with new races, advanced classes, occupations, feats, creatures, and rules for organizations and secret societies.  The expanded magic system features new magic items for the modern world.   

June

Ghostwalk, by Monte Cook and Sean K. Reynolds.

Ghostwalk is a campaign setting for D&D, an undead city which allows players to interact with and play ghosts as tangible characters for the first time.

Hero's Guide, by JD Wilker and Rodney M. Thompson.

Hero's Guide is a Star Wars accessory that provides new options for characters of all classes. 

August

Dragonlance Campaign Setting, by Margaret Weis, Don Perrin, Jamie Chambers, and Christopher Coyle. 

This book, produced by the Sovereign team as part of the broad-ranging Dragonlance deal (see 'Weis and Perrin To Write Dragonlance for WotC'), updates the Dragonlance setting to the d20 rules system. 

Galactic Campaign Guide, by JD Wilker and Richard Baker.