There are many places to look when purchasing outdoor halloween decorations. There are local halloween specialty stores, wal mart, target, hobby lobby, joann, michaels, and many more.
There are many sites to give you cheap ideas. Some of them are www.halloween-website.com/decorating.html and www.bhg.com/halloween/outdoor-decorations/
A great resource for hade-made, unique Halloween decorations is http://www.halloweenmonsterlist.info. All links are updated, verified, and has an easy to follow guide to ensure you find exactly what you're looking for.
I like shopping at Kmart, Target, and Walmart for outdoor Christmas decorations. However, their stock may not be out yet. Check their online counterparts or Amazon for some 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/).
Spooky halloween decorations would include things such as ghosts and ghouls. Try party city or your local party store to find spooky halloween decorations.
A stylish decoration that can be used for both Halloween and Christmas would be lighted green topiary. These are great in entryways and can be used year long. During Halloween, bats and pumpkins can be hung from branches. While during Christmas, simple colored bulbs or other ornaments will show the seasons spirit.
There are several party stores that will have Halloween decorations. Try going to Party City. If you don't find what you are looking for there then try going to Michael's
Making your own Halloween decorations can be a lot of fun and it doesn't have to be expensive. Some great places to get ideas are http://iblue.hubpages.com/hub/Top-10-Halloween-Homemade-Decorations, http://familyfun.go.com/halloween/halloween-crafts/, and http://www.squidoo.com/halloween-homemade-decorations.
spirithalloween.com is the one stop shop where one can find cheap Halloween decorations. If it wasn't for this site most people will become broke for buying Halloween decorations.
To find the best Christmas outdoor lighting for your needs, you will find the best selection at http://www.theholidaylightstore.com/store/cart.php. Their knowledgeable staff will answer your questions, and even schedule an appointment to help assist your set-up.
You can find Halloween decorations at your local mass merchandisers such as Wal Mart, K Mart, Target and Kohls. Almost all retailers distribute halloween decorations throughout the fall season!