A ZMATH Suggestion, from Neil Eastep
May I present a recent find:
ZMATH - The Zentralblatt MATH Database The ZMATH Database contains about 2.3 million entries drawn from about 3500 journals and 1100 serials from 1868 to present.
ZMATH costs about USD $90 for a personal subscription, and has been invaluable to my work over the last couple of weeks that I have been subscribed.