WordPress has a feature built-in that many people do not know about. It’s called Link Paste.
Typically when you insert a link you will highlight the word(s) you want to link and then click on the link icon in the TinyMCE bar.
How does a simple copy/paste sound?
Copy a link, like http://www.photocrati.com using either command+c on a Mac or control+c on a PC.
Then in a blog post or page, highlight a word, or a few words.
When highlighted, use command+v on a Mac or control+v on a PC to paste the link for those words.
What you should see is the words linked like you used the TinyMCE link button.
Note this will only work in the visual editor, not in the text editor.