Here are a few gift ideas for different scenarios.
For the referrals, less than $5 value:
Starbucks, carwash, itunes card, Ice cream, quote books (amazon .com has tons of stuff), magnifying glass mirrors, any small trinket I can find! Lotto tix
For the rotating gift of top 40 every past clients 3 months (approx.)
Leather passport holder , luggage tags (potterybarn.com), books, magazine subscriptions, anything that relates to their interests
Cups with logo, book (think/grow rich) with my name on it.