Full Domain Hosts at No Cost!

These are a great idea for learning about design, or even for a vanity email (you@whateveryouwant.com) without the monthly fees. You do still have to purchase the domain name, but honestly the prices for .coms etc have fallen so drastically since I began, it's really not a big expense. Godaddy and many others often have specials where you can get a name for around $7 a year! Many of these however will want you to register with them. Since that's their only way of making money, that's more than fair :)

DotEasy.com Free Domain Hosting
Their free hosting package gives you 100 megs of storage, 1GB/month of data transfer, up 10 personalized email addresses (ie. yourname@example.com, sales@example.com etc.), FTP access, free setup and no monthly or hidden fees.

They also offer many low priced packages if your site needs more space or bandwidth but you don't want to have to spend a lot. Again at the time of this review (their prices may have changed since) their Ultra Hosting package starts at $7.95/month and includes 1000 MB storage, 20 GB monthly traffic, 100 email accounts, PHP / MySQL / CGI /SSL / Frontpage etc. The also have an unlimited account that starts at $7.95.
Forced Ads: None, it's ad-free.

Host-ed.NET
The biggest thing that makes this host stand out for me is that it's green, yes, I do mean environmentally friendly, that alone is awesome!

They have a few different plans available including paid hosting, but since you're looking for a free home for your domain I'll only explain that one right now. It offers 250MB of disk space and 5GB data transfer monthly as well as 1 domain, 3 subdomains with FTP access, a control panel and a web based file manager. Other bonuses are pop 3 email, 1 MySQL Database, PHP 5, Perl, CGI and traffic stats. I also could find no mention of ads being placed on your domain.

FreeHostia
Register a top level domain with them for $9.95 and they give you free domain hosting with 250MB space and 6GB monthly bandwidth. A few bonus features are an easy 1 click installer with many popular scripts available, up to 5 domains and 15 subdomains in the account, Perl and PHP with 1 MySQL database and PHPMyAdmin, FrontPage extensions, SSI and many others. Again, I haven't had a chance to test this host (I can only run so many domains at a time ;-) ), but it does look like a good one.
Forced Ads: Nope.

Mister.Net
To get free hosting here you must register your domain through them (which is not free). That said, they have "No setup fees, No forced advertising, No banners, No popups, No fine print, No contracts and No hidden charges. Not now. Not Ever!" My sister hosted her website here and said the service was great. Their free domain hosting package gives 250 MB disk space, front page extensions, personal cgi-bin, unlimited email accounts, 5 pop mail accounts, 5 Gigs of bandwidth per month, unlimited ftp access, web based site control panel, domain control panel, accept credit cards worldwide, free e-commerce/shopping cart and more. Worth looking into!
Forced Ads: None.