Sarah,
It`s Ok to have limits. Figure out what your budget is for donating. Divide that into the four quarters of the year. Say as an example, that it fits your budget to apply 12 items per year right now. During the first quarter you set aside three items for charity. If you get only three soliciations then you`re covered. Anybody else that approaches will have to understand that you`re sorry that you can`t offer anything right now and that you have a strict budget that you adhere to which allows you to give regularly throughout the year. It really is the responsible way to give. (Unless you are an entirely wealthy and senseless penny-pinching miser, of course! 
I`m just guessing but I really believe that if more people adopted this responsible practice to all of their charity offerings, there would actually be more people giving regularly than just saying no.
Sarah, I`m really glad that it works for you.
By the way, your website is really nice. I think I`ll have to consider using it. I`ve used a company that rhymes with ummmm.....Ted Bentelope (Don`t want to advertise the competition ....you know that rhyme is impossible!) several times to send little things to my wife. I`m sure you are familiar with it as it is a hugely successful gift business. But I have to say. There is no reason to not look into yours. Thanks!
I can tell you what I
do and you can feel free to use or not use what works for you.
I look at and deal with charities the same as I do those annoying toner sales
guys or people who cold call to sell you something like long distance.
I make my decisions on whom I will be donating too a year in
advance (or I only evaluate my venders once a year and choose them for the
entire year.) I am happy with my current charity (or vender) and I am not
looking to give more (or replace them). However if you would like to be
considered next year please send me your contact information along with any pertain
information you would like me to review.
I never give to anyone who can not tell me how much of every
dollar raised will be used to actually purchase medicine, buy food, pay for
blankets etc. A lot of the so called charities take 80 cents of every dollar to
pay themselves and only 20 cents is used for the actual advertised purpose that
to me is immoral.
Good luck,
Eric

Hi Sarahleighm,
You are correct the more you give the more you get asked. I believe they sell the donor list to companies other companies. (Something I call the old double dip or the twofer)
I am glad my advice was helpful, it’s never easy to say no especially to a charity they always seem to know what to say to get you to want to donate, however the simple fact is its not possible and should not be expected.
You’re the boss be selective that way you can get more involved in those charities like if you wish, like hold fund raisers for them, give the charity access to your employees by allowing them to come in once a year to ask for donations, by encouraging your employees to donate volunteer time, you can pay the employee if he donates 4 hours of his time to charity each month, etc, etc, on, and on...
All things you can do only if you only deal with a select few charities. If you have too many charities your employees will get tired of having to be asked for money every few weeks, no focus to attempt to organize an employee volunteer day or program.
Have a great day,
Eric
The continual request for freebies and donations has been a big problem in the scrapbook industry. It`s gotten to the point that anyone having a few friends over to scrap thinks that manufacturers ought to send freebies for goodie bags. Most companies have pulled way back. I have talked to a few vendors who said they don`t see an increase in their business from it. So, they have approached it from a charity stand-point rather than an advertising stand-point. So, they donate to causes they support now, rather than big events they think will give them a ROI.
A couple of manufacturers have a "donation request" form on their site that people fill out. They make it clear that they are not going to fill every request, but will consider them and let you know. One alloted so much product per month and when it was gone, it was gone.
I agree with Chris - cute site!
~Kim
ScrapBiz