Haloween is one of the most popular decorating holidays their are. If you want it really scary, I suggest going for a realistic theme. Maybe some caution tape with some fake blood and chalk outlines.
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.
You can find decorations for your door online at this site: http://holidays.thefuntimesguide.com/2009/09/halloween_decorating_ideas.php. It has lots of ideas, as well as some videos of ideas, not just for decorating the door, but for decorating other areas of the house.
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/).
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!
If you're looking to decorate for Halloween with your friends and family, and stay on budget, this site will provide you with numerous tips on how-to decorating and DIY tips. Please visit http://www.wikihow.com/Decorate-Your-House-for-Halloween-on-a-Budget to see what ideas are waiting for you.
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
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 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.
One can find decorating ideas for a country cottage from many places. Some of the best sites to find decorating ideas are country living, house to home, decorating ideas made easy and many more.
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
You can visit Youtube to find various ideasfor your Halloween party. You can also visit Michaels art store for a large selection of Halloween ideas, themes and supplies.