Trashmail.net went pay-only (because of spammer abuse!) last summer, and I only discovered it recently as I don’t use these services all that much. During the search for alternatives, I found new ways to search for alternatives.
The service AlternativeTo has always been a good place to go for desktop software alternatives; now they include mobile platforms and online applications as well. The list of alternatives to TrashMail is extensive and interesting.
The other interesting item is Google’s related: operator. This can be used during searches, but at the bottom of a search there may be a link to sites similar to the one searched for. In the case of Trashmail.net, Google returns a lot of alternatives.
As an ironic twist, consider this: Google has a list of sites similar to AlternativesTo.net.
UNIX Administratosphere 
In my opinion, the best disposable mail address is Gmail. How so? Creating a new account takes you only less than five minutes and you can use the new address until it gets too many spams, though you hardly see them in your inbox. When you are ready to dispose the mail address, do Gmail a favorite, delete your account.
If you are a Firefox user, create a new profile for using that Gmail account. Anytime, you need to access the inbox, you fire up firefox with –no-remote, so you can have two instances of Firefox. You click on confirmation link, then delete/archive the mail and close the Firefox.
You wouldn’t need to create a disposal address on a disposal email service provider’s webpage, then copy and paste that email address you couldn’t memorize in a second. When you fill in a form, you just press down arrow key to get your disposable Gmail address which you have entered before.
The best thing is Gmail address is hardly being rejected. Many websites block disposable address.
That’s an interesting idea. However, many disposable email services also provide browser extensions that allow you to generate an email address and fill it in automatically while forwarding to your real address. Others provide you only with the domain address and provide you with the ability to choose any “username” at all without restriction (and point you to a publicly accessible web page for mail retrieval).