There are several websites I think is helpful to me when I get stuck for ideas:
http://cleanandsimplestamping.blogspot.com/ This is where I go to for really clean and simple card layouts- as their name would suggest. I really gravitate toward this style and you may find it helpful.
http://www.splitcoaststampers.com/ This is a community of stampers that have gotten together to create this wonderful website- there is a gallery with all stampin' up samples categorized by name as well as personal and other company albums (my user name is LyndaLee28 if you want to check out my gallery) and forums with discussions of all things stamps. You can subscribe to this and they will send you emails every Wednesday- I spend WAY TOO MUCH time here......
http://www.stampinup.com/ca/enc/default.asp They have the entire Stampin' Up catalogue and current mini catalogues on line for those of you without one- Mine is vinyl covered to prevent any drool from damaging it! I go to my SU idea book and catalogue everyday for color ideas and layout from their samples- often altering the set that I use and using one color combo with a different layout makes it look totally different.
There are so many others but I think this is my short list. Inspiration is everywhere -in catalogues, websites, stores, even nature. I am always cutting out pictures from magazines and flyers from Target, Gumps, Nordstroms, Gap, Pottery Barn for their interesting and trendy color combos and jotting down things in scrap pieces of paper that I later say- what was this? OH yeah! I wanted to try that...... So look around you.