NPC Designer is perhaps the most advanced npc generator available for the 3.5e (d20 OGL) game.  It is easy enough to use that you can be creating non player characters within seconds after installing yet more then enough functionality available to make it fit perfect for your game.

NPC Designer Features

Races: All of the base SRD races are included.

Monster Races: You are able to create non player characters with classes and templates for monster races like dragons, demons, devils, dragons and many others.

Advancing Monsters: You are able to advance monsters with ease.

Epic: While the code is in place scripts skill need to be complete

Racial Paragons: You are able to select for the races it is available.

Bloodlines: One of the few applications able to handle bloodlines.

Templates: You can select a single template to be generated for a non player character.

Classes: Each non player character can have up to 4 classes selected.

Prestige Classes: In addition to the 4 classes, you can also select 4 prestige classes. The requirements needed for the prestige class will be taken into account during the generation process.

Skill Selection: It goes well beyond just random selection, it takes things like background , race and region and past selections into consideration.

Feats: Go beyond just normal feat requirements, you can also design your own to fit your world or use them to enhance the generation process.

Spells: Add your own and have them selected intelligently based on alignment, god and even feats. You can also create spell chains to further enhance the selection process.

Stat Block: NPC Designer includes a few different stat block formats, including those specifically for other applications (Fantasy Grounds and DM Genie). Stat blocks are scripted so you can alter or create your own

Game Ready Cards: NPC Designer has its own 3x5 card format for every NPC it creates and exports them as an image or print.

Designer Screens: Have the perfect NPC in mind for your next session? Use the designer screens to select what feats, skills or equipment your non player character has and let NPC Designer handle the rest.

Equipment: Equipment is generated for the NPC based on class and level, you can also have equipment selected based on race, alignment and many other factors.

Constant Development: NPC Designer is unique compared to most software products available today, not only does it offer something different but also the way we approach development. Even though NPC Designer is available for free, new features and functionality are still being developed from time to time.