I like to use the Better Homes and Gardens website for my decorating ideas ( http://www.bhg.com/halloween/outdoor-decorations/ ). The great thing about this website is that it doesn't just give you Halloween ideas, but it has ideas for every holiday!
A good place to find do-it-yourself ideas for decorating an entryway for Halloween would be www.doityourself.com or at a local craft store.
I know of two really good places to find ideas for decorating Halloween treat bags. You can find them at Party City. I'm not sure if you have one near you but I'm sure they have a website. Also, Oriental trading Company. They are a catalog company with great ideas.
Using old Christmas balls for Halloween is a unique idea. For additional information about decorating, please see the following website: holidays.thefuntimesguide.com/.../halloween_decorating_ideas
Martha Stewart (http://www.marthastewart.com/photogallery/halloween-decorating) has a plethora of tips and tricks for Hallowe'en decorating. Better Homes & Gardens also has a large selection of ideas, though they focus more on outdoor decor (www.bhg.com/halloween/outdoor-decorations/).
Better Homes and Gardens have several pumpkin decorating ideas without using knives nor carving your pumpkin up. You can learn how to apply their techniques by visiting their website at www.bhg.com/halloween/pumpkin-decorating.
You can get ideas for decorating a bunk bedroom from the website called Housetohome. You can also find ideas on the websites of manufacturers such as Dulux.
Sites such as HGTV and House Beautiful are known for home decorating and designing ideas. With lists of decorating ideas and examples, they are two top options to visit.
I try every year to get good decoration ideas and I always browse around. Here is a good site that has many great ideas. http://www.hgtv.com/topics/halloween/index.html
There are many great websites to find affordable ideas for Halloween costumes! Here are a few links: www.robinsfyi.com/holidays/halloween/costumes.html and familycrafts.about.com/cs/halloweentheme/a/091399.html.
If you are looking for unique costume ideas, you can find them at http://www.essortment.com/halloween-costume-ideas-50-unique-weird-ideas-52253.html. You can also find unique decorating ideas at http://www.halloween-website.com/decorating.htm
Party city offers great unique halloween decoration ideas. They always have up to date costumes and party supplies for every occasion. They also have catalogs to help with decorating ideas.