I find http://www.sprymedia.co.uk/article/Design Design to be really handy when I'm making sure text line cadence is right. It's handy all around for design: powerful grid, rulers, measuring, and targeting tools.
http://westciv.com/xray/ XRAY keeps a spot on my bookmark bar. It's an HTML-traversing bookmarklet that lets me figure what's going on with underlying HTML and positioning CSS without leaving the page. It's been somewhat marginalized since Safari's Web Inspector started rocking so hard.
They; InstaPaper (also great); and Delicious/Facebook/Yahoo Bookmarks share/post bookmarklets are what currently dominate my bookmark bar.
http://westciv.com/xray/ XRAY keeps a spot on my bookmark bar. It's an HTML-traversing bookmarklet that lets me figure what's going on with underlying HTML and positioning CSS without leaving the page. It's been somewhat marginalized since Safari's Web Inspector started rocking so hard.
They; InstaPaper (also great); and Delicious/Facebook/Yahoo Bookmarks share/post bookmarklets are what currently dominate my bookmark bar.