An interesting feature is that you can search title, tag or even handwritten/printed text in an image. This is not true with many different search engines.
You can download Evernote on your Mac/PC or get the free application for iPhone/iPad and Android. If you buy the premium version ($5/month or $45/year), you can search PDFs, upload up to 500 MB per month (the free amount is 40 MB/month), receive an added layer of security (SSL encryption) and upload virtually any file type to the application (think Microsoft Office documents, videos, etc...).
The mobile application is very similar to the desktop application, only much more streamlined. When you open the application, you can create a new note, view all notes, see your favorites or sync with other devices and the web. Notes can be in the form of text, picture/video or voice notes. Your notes are geotagged for even more help in remembering tasks. To save as a favorite, simply click the star next to the name of the note on each note.
I have heard of people using this application for everything - for remembering where you parked your car with a photo note to keeping a grocery list. This application is a lot like Dropbox in that you can store/share/sync files with multiple devices, only this one is aimed more at little notes, reminders and photos than serious file sharing, but you can do that too. The only improvement I would make to this application would be to make text out of my voice memos, like Dragon Dictation.