Here is a fabulous garlic rosemary olive oil recipe:

Ingredients

* Olive oil
* 6 cloves garlic, minced
* 4 or 5 sprigs fresh rosemary

Directions

Mince the garlic and drop into a clean dry bottle. Placing the rosemary on cutting board and using the back of your knife hit the rosemary like you were trying to tenderize it. This is exactly what you're doing, bruising it so the oils can get out. Next slide the rosemary into the bottle with the tops first, that way they'll come out easer when you refill the bottle and replace the garlic and rosemary. Let it set a day or so and it's ready.

Find it at http://www.recipe4living.com/recipes/garlic_rosemary_olive_oil.htm

Here is a link that might be useful: Recipe4Living

How long can you keep the oil. I read somewhere, no longer than 3-4 days. Also, do you keep in on the counter or in the fridge?

Check out the Haravest Forum. There are some very knowledgeable members who could answer your questions. My understanding is that homemade flavored oils are dangerous unless used within a day or so and must be refrigerated. Definitely not something for gift giving. Herb flavored vinegars are another matter. They are safe if produced carefully. Here are a couple of informative pages from university extension web sites:

http://www.ext.colostate.edu/pubs/foodnut/09340.html

http://www.uga.edu/nchfp/publications/uga/uga_flavored_vinegars.pdf

There's a lot of misinformation and outdated information on websites and blogs. If you want the safest and most up-to-date information, find a reputable source, mainly a university extension, the National Center for Home Preservation, or the latest Ball canning book.

Here is a link that might be useful: Garden Web's Harvest Forum

I agree with Shambo, flavored oils are not something for the home cook to try or give for gifts. If you want to make up some foods for gifts, look at herbed vinegars, jams, jellies, and chutney. They are all pretty easy and can be sealed by processing in a boiling water bath for long term storage.