The Arctext command in AutoCAD Express Tools allows to draw text along an arc but if you need to align your text to a polyline, spline or ellipse, there is no standard tool for this.
Andrzej Gumula has written the CurveText LISP utility which solves exactly these situations. Load the CurveText.LSP file and start the CURVETEXT command. Select a polyline and specify the text and its alignment parameters (offset, height, displacement, startpoint, etc.). The CurveText utility places the individual characters of your text so that they are meandering (flowing) along the selected curve. It also groups the characters together again.