available

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Present and ready for use; at hand; accessible.
• adjective Capable of being gotten; obtainable.
• adjective Qualified and willing to serve or assist.
• adjective Chemistry Capable of being used in a chemical reaction.
• adjective Botany Present, as in soil, and capable of being used by plants as a nutrient.

from The Century Dictionary.

• Profitable; advantageous; having efficacy.
• Having sufficient power, force, or efficacy for the object; valid.
• Capable of being used or employed with advantage; attainable; accessible; at one's disposal: as, his resources were not available at the time.
• Advailable is a rare and obsolete form.

from the GNU version of the Collaborative International Dictionary of English.

• adjective obsolete Having sufficient power, force, or efficacy, for the object; effectual; valid.
• adjective Such as one may avail one's self of; capable of being used for the accomplishment of a purpose; usable; profitable; advantageous; convertible into a resource

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Such as one may avail one’s self of; capable of being used for the accomplishment of a purpose.
• adjective Readily obtainable.
• adjective law Valid
• adjective archaic Having sufficient power, force, or efficacy to achieve the purpose; availing, effective.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective obtainable or accessible and ready for use or service
• adjective convenient for use or disposal
• adjective not busy; not otherwise committed