Send an iMessage from almost any application
Apple's sharing services allow you to send an message from many applications other than the Messages program itself.
If you use Apple's iMessages service to communicate with friends and colleagues, then you might regularly open the program either in iOS or OS X to compose your message.
Apple offers some sharing services that interface with Messages, which if supported in the program you are currently using, can be taken advantage of to send a basic message to any of your Messages contacts.
These sharing services are intended to send a selected object, be it an image in iPhoto, or a file in the Finder, or some text in a program like TextEdit. When invoked, these services simply append the selected items as attachments to the message. Therefore, if you simply delete the attachment, then you can type whatever alternative message you want, and send that instead.
For example, in the Finder you can right-click any file or folder, and choose Messages from the Share submenu. When you do this, a small messages window will appear with your item selected, so simply delete the item, and you can now address and compose the message accordingly. If you are using TextEdit, then you can similarly right-click a word to access the same Share menu, in which you should have Messages as an option.
This option is available either on iOS or OS X, so wherever you see the sharing menu with an option to compose a Messages message, then you should be able to remove any attachments and send the message to anyone.