There were two Banjo games for the GBA called Banjo-Kazooie: Grunty's Revenge & Banjo-Pilot and Grabbed by the Ghoulies was a spin-off of the Banjo games (I.E. the fish from the Banjo games, Roysten, makes an appearence. That, and theres tons of pictures of Banjo and Kazooie, as well as other Rare characters, like Mr. Pants. Even Fox McCloud has a quick cameo in a portrait, but as a Werewolf. Sorry, I know I spelled that wrong). Sadly, none of them had much success. I played BK: GR, and I didn't like it that much. Then again, I didn't play it long enough.
GbtG was very good, though, despite harsh criticsm. Definetly a very underrated game.
As for a new Banjo game, one was announced in a british Xbox mag (along with another sequal to a Rare series, Killer Instinct) for the Xbox 360, and EGM has said that there are rumors of one being developed for the Nintendo DS.