Title attributes are ignored.
On the other hand,
alt attributes do (at least sometimes) carry some weight.
For instance, if you use graphics for a menu system or you otherwise apply an <a href> link to an image, the alt attribute will stand in place of the normal link anchor text. Link anchor text is known to be an important factor in ranking -- the jury is out as to whether the alt attribute text carries the
same weight as the equivalent link anchor text, but it does appear it has a reasonable effect.
Google seems to go back and forth as to whether they count the alt attributes of unlinked images. Honestly, I'm not sure which way they're going with it these days.
But in any case, I use the alt attribute for accessibility purposes, so it generally has a bit of descriptive text in there that usually will naturally contain a keyword or two. If Google decides to count it, great. If not, I wasn't creating the attribute for SEO anyway.
I wouldn't just stuff them with a list of keywords because of the usability/accessibility implications, but IMO there's nothing wrong with working a few key terms in there.
--Torka