All outputs on this page are IMGs.

<div class="line">
	<img src="print.png">
	Some text
	<input type="button" value="Input Button" />
	<span class="spn">Span</span>
	<select><option>Select</option>second</option></select>
	<button>Button</button>
	<input type="submit" value="Input Submit">
	<img src="print.png">
</div>
<style>
	.line{height:50px;}
	img,input,select,button{vertical-align:middle;}
</style>

FF3 IE6

<style>
	.line{height:50px; line-height:50px;}
	img,input,select,button{vertical-align:middle;}
</style>

FF3 IE6

<style>
	.line{height:50px; line-height:50px;}
	img,input,select,button{vertical-align:middle;}
	* html button{line-height:1;}
</style>

IE6

<style>
	.line{height:50px; line-height:50px;}
	img,input,select,button{vertical-align:middle;}
	* html button{line-height:1;}
	* html .spn{display:inline-block;height:50px;}
</style>

IE6