At the Chicago Home Expo Monday, throngs of voracious Midwesterners descended on the State Farm Insurance booth to grab free promotional nail files. 'Lookthey have the State Farm logo printed right on them,' said Beth Hoffman, 37, a Zion, IL, mother of four, as she clutched a handful of the complimentary items. 'I'll grab a few extra for Mom. I'm sure she could use a couple, too.' The horde of freebie-seeking Midwesterners then moved on to the Century 21 real-estate booth, where they plundered a basket filled with free business cards that turn to sponges when dunked in water. 