I'm assuming you mean the alt attribute used in the image hyperlinks. Yes, they help SEO wise but also browser wise. If a visitor has images turned off, using a text browser or screen reader they won't see anything for your image. The alt attribute would be displayed in these cases. Also, it helps with your Google Images SEO as well has the image file name. You find it is also a good way to get keywords into your webpage. Meta tags are useful to most search engines. Google for instance does not read keyword meta tags, but it does read title, description, etc. If you do not display a description meta tag then Google will generate one from your page. My personal rule of thumb is to use majority of the availible meta tags, you never know what primative search engine might jump into the spot light.
Hi Brian, They will help your rankings when used appropriately and properly. Many people make the mistake of looking at HTML purely from an SEO point of view, when in fact they should be looking at the semantics of the elements, attributes and values they are using. As ssandecki said, image elements need the alt="" attribute in order to provide alternate information to identify what the image is about to those who cannot see the image, such as screen readers and search engines (not to mention users of the text-based browser Lynx). As for meta tags, most of them are pretty useless. The only ones I consider to be of any use from a search engine's perspective are the keywords tag (just barely, though, think "is that a spec of dust on my screen or a blip on the radar?") and the description tag - the description however should be used to draw the visitor to your site (make him or her click on that link) rather than being stuffed with keywords. You want to make sure that the description tag is used appropriately - it is afterall going to affect the first impression your visitors are likely to make of your site. Also remember to use individual descriptions and keywords on each page of your site (rather than a blanket that covers the entire site). The home page is no exception - optimize them for that page, not the whole site. Anything other than that (as far as META tags go) can be taken care of via a robots.txt file. Also please note that <title></title> are not meta tags, but meta-information (not to mention an actual distinct HTML element).