A great source is the website of a fella that you will see in threads here.
http://www.lee-mac.com/index.html
Lee Mac even has a nice search engine for his code as well.
CADTutor is another: http://www.cadtutor.net/
(defun c:mymtext (/ txtstr pt)
(if (and (not (eq (setq txtstr (getstring t "\nEnter a really long sentence: ")) ""))
(setq pt (getpoint "\nPick the insertion point for the text:"))
)
(entmake (list '(0 . "MTEXT") '(100 . "AcDbEntity") '(100 . "AcDbMText")
(cons 10 p)
(cons 40 (* (getvar "DIMSCALE") 2.0))
(cons 7 (if (tblsearch "STYLE" "Standard") "Standard" "Standard" ))
(cons 1 txtstr)
)
)
)
(princ)
)
The if / and tests the entry to make sure it isn't just a return and that txtstr is set to something.
Copy / paste the code into the AutoCAD Visual Lisp Editor, found on the Manage Tab.
From the there, you can use the Tools / Load Text in Editor to test.
Once happy, save the LSP file and put it in your Startup Suite, or save to AcadDoc.Lsp to load it automatically (which needs to be in the Support Paths or current drawing folder), or manually load at the command line: (load "Filename.LSP")