Foxcloud, the maker of Foxmarks even offers free hosting for your bookmarks in a one quick step the first time Firefox starts after installing the extension. Just enter your name, e-mail address, the desired username and password and it’s done.
It will upload your current bookmarks to foxcloud.com. Another benefit of using Foxcloud hosting is the ability to access your bookmarks even when not using the extension or with another browser through my.foxcloud.com.
Once up and running, Foxmarks will check for changes in your bookmarks every minute and if detected synchonize them with your remote bookmarks.
Some tips based on currently reported bugs: avoid using slashes (/) in your password, don’t use an e-mail address of more than 32 characters.