Some of us use myemail+sitespecific@gmail.com. It gets delivered to the same myemail@gmail.com. Other mail providers probably offer the same convenience.
Some nasty login forms block the '+' symbol from being used.
I sometimes use multiple dots to create an alias, but it only works for a fraction of e-mail providers (i.e. GMail). E.g.: example@example.com is the same as exa.mple@example.com.