iPhone/iPod touch only: Free application O-Marks automatically syncs bookmarks to your iPhone from Firefox-syncing tool Foxmarks or from your Delicious account. The most intriguing feature for Firefox users is the Foxmarks integration, since once you've set up O-Marks with Foxmarks, your Firefox bookmarks now automatically sync to your iPhone. That means you don't need to use Safari just to sync bookmarks to your iPhone anymore. It just takes a little know-how to get it set up.
If you're not already a Foxmarks user, you'll need to install the Foxmarks extension and register for an account. Assuming you've done all that (and downloaded O-Marks), here's how you set it up on your iPhone.
First, login to your Foxmarks account on your desktop. O-Marks needs a unique RSS feed of your bookmarks to work, and while Foxmarks provides this functionality, you have to turn it on. To do so, click on one of your Foxmarks folders, then click the Share button on the site's toolbar. You'll see a pop-up window prompting you to share this folder. Assuming it's a folder you want to share, tick the checkbox. Foxmarks will automatically create an RSS feed for that folder that looks something like:
What you need is to copy the key at the end of the URL (in my example, the 10 x's).
Now fire up O-Marks on your iPhone. By default all the bookmarks are set to Delicious' popular feeds, so you need to edit them. Tap the 'i' button on the bottom right of the screen, then tap on one of the categories. From this screen, you can edit the feed name, switch over to Foxmarks, and enter the Foxmarks RSS key we created above. Once you've done that, just save your settings. When you go back to O-Marks, it'll automatically download the bookmarks from the folder you set up and put them right in front of you. Unfortunately these bookmarks don't integrate with Safari, inasmuch as you can't access them from Safari—instead you launch Safari whenever you tap on one of the bookmarks in O-Marks.
The application could use a bit of polish, but it still does exactly what it says (i.e., uni-directional sync), and it does it well. If you wanted to take things a step further, you could set up a dedicated iPhone folder in Firefox, share that folder with Foxmarks, and have quick synced access to those bookmarks whenever you wanted. Alternately, you could set up O-Marks with an RSS feed of all your Delicious bookmarks tagged iPhone—which again would put them at your fingertips whenever you started up O-Marks. Not bad.