Also see URL Redirection

DHS - Offers domain redirection, and static & dynamic DNS services:
(1) Redirect your domain name to another site with cloaking (in a frame - no ads yet).
(2) Static hosts & domains - Free third level hostnames and domains.  By using a static host you can point a hostname to an an IP address.  With a static domain you can specify the MX (Mail Exchanger) record, and have subdomains point to multiple machines.
(3) Dynamic DNS - allows people who use dialup modems or whose IP address changes frequently to still have a hostname point to their machine.

DomainRedirect - Free domain forwarding (redirection).

GraniteCanyon - Offers both primary and secondary DNS, and MX records for all of your domain names.  Unreliable.

No-IP - Offers dynamic and static dns services under various top level domains.  You can run your own server and use one of their domain names (8 choices) for your IP address (you can also set the MX record). The dynamic dns service also offers a downloadable client that keeps track of your changing IP address.  They also offer free web redirection under the hopto.org domain.

VDirect - Domain and email redirection, with cloaking and visitor statistics.  Choose banner-bottom, popup banner, or banner delay page.

ZoneEdit - Recommended.  Free DNS, domain forwarding, email forwarding, and domain parking.  Also you can get your own nameservers and your own control panel to complement your firm's existing website. Give your clients secure access to only their own domains, and they'll save you time and money by editing their own DNS entries.  Free use for up to 5 domains.*

* There is a bandwidth limitation per domain per year of 200 megabytes of total data transferred through our servers. Usage that counts towards your quota includes bytes transferred during DNS queries, delivery of parked home pages, delivery of URL forwarding information, and delivery of forwarded e-mails. If you do not use WebPark, WebForward and MailForward, then only DNS queries will count towards your total usage.  If a single domain goes over 200 MB of transfer during a year, then it counts as TWO domains, if it goes over 400MB, then it counts as three, etc. Usually DNS hits are cached, so even the busiest sites won't go over the 200 MB limit. 200 MB should get you about 1,000,000 DNS queries. A typical site uses 5 MB per year of DNS bandwidth.