The Form Panel module provides two theme functions which, in turn, provide an easy way to put multiple input form elements on the same line. At the most basic level, it can turn this:
First Name: Last Name:
[textfield] [select list]
It can do this using either an HTML table or
<div> tags. In both cases, it includes various CSS classes to help with styling.
It is important to note, however, that this module does nothing on its own. You must refer to one of the included themes from PHP code in order for there to be any effect.