Better editing tools for techno-laypeople

Client after client is having me move their site into WordPress so they can edit it themselves. I resisted this for a long time, remembering curious and ambitious clients who mucked in their HTML and put blinking neon green headers up and 8MB snapshots of Aunt Dora’s 81st as well. But there was no resisting the tide, and WordPress certainly does have its advantages. I came to terms with WP as a CMS a couple years ago, but still have one problem bothering me. My clients can edit their sites, but they don’t have the tools to do it well. They can’t add margin around a photo. They can’t add columns. The only styles I can predefine for them are header tags and blockquote tags.

I’d like to find some plug-ins that give my clients a few more formatting/layout options when the create their posts and page text. Can anyone recommend any particularly good ones?

Thanks.