Pollen Levels is a gadget for Google Desktop or iGoogle personalized page. It shows the 1-day and 4-day pollen levels for your zip code as given by Pollen.com.
Below are some of the user reviews:
"The pollen forecast really helped me prepare for my seasonal allergies. I was able to plan for when to take medication before my symptoms acted up. I can also check the pollen levels for when I'm traveling."
"Great tool! I have it set up on both my home and work computers, with each set to their local zip codes. It’s interesting to see the difference in the Pollen 4-day forecast between these 2 areas."
References:
Featured Gadget: Pollen.com - Pollen Levels. Inside Google Desktop, 02/2008.
Interactive Allergy Map by Greer Labs. Click your state to find region-specific, common airborne allergens there.