Rikai is a great dictionary for translation, but translating dictionaries should only be used if there is not enough time or context to figure out the meaning of a word. Ideally, you should go to an English-only dictionary and use the bilingual dictionary only as a last resort.
So get your students away from bilingual dictionaries by using an online English-only dictionary. Not one with just text, but one with graphic representations of meaning. I’m talking about Visuwords.

Enter a word into the box, and a whole sematic web appears below. The connections are coded and you can move them around, get definitions by hovering over the words with the mouse, and use it in many different ways. People remember vocabulary by connecting a word to other words. Trying to remember words in a list is one of the worst ways to learn new words, second only to flash cards. Lists and flash cards help you to forget words. Using words in sentences and linking them to other words is the way to build a vocabulary. This tool works like your brain does.

You can buy a memory stick now for very cheap. I bought a 2 gigabyte stick 3 years ago for 20,000 yen. Yesterday I bought a 16 GB stick for 4,000 yen. Most people would never use more than 1 GB. But if you start using audio or video files, the sticks can fill up fast. If that is the case, try a portable hard drive. They now cost less than 10,000 yen, and give you 120-320 GB and more. This is a great way to back up your laptop, or carry it instead of the laptop when you visit friends with computers.
