The logo must not look too glitzy or bold. It needs to be understated, simple, in one or two colours, no gradients, tints, shadows etc.
It needs to convey honesty, trust, growth, gift giving, happiness, benevolence, integrity, novelty. It will be used to market many differtent types of products from many different charities and so needs to be neutral in terms of product type and purpose it will be used to sell. It will also be used on pages that will contain charity information, so as a brand, it needs to be neutral enough to not take away from the charity branding.
I like the logo used here: www.charitycards.co.uk (bird and envelope). I also like the simplicity and neutrality of the Spotify logo (www.spotify.com).
I also like the idea of trees or growth, as in an idea which is about charitable gift giving, plant a seed of good now, and it will help people in the long term. e.g. http://www.logoking.com/indetail.php?id=160
but with a more obvious link to gift giving.
Definitely don't want anything that's too arty, girly, complex, pictorial, or cheesy. Just something plain, simple and honest. It should be styled to be more for a european market than a US market.