How long will you be away for? Where will you be going?
Some parts of the world have photo shops where you can burn your images onto a CD. If your destination is not too "ulu" you may already have enough storage.
Getting a 256MB card will let you shoot 240 images in total. Depending on how you shoot and how long you will be away for, this may or may not be enough. Only YOU can decide whether it's enough, none of us can advise you on that!
If you're going to an ulu place for a long time, consider investing in a digital wallet - that's a portable HDD with battery and CF reader.
A lot of times we go out buying lots of memory for that BIG trip we take maybe once every 2 years. The rest of the time the memory cards are sloshing around the bottom of the drawer. Digital photography is very popular these days, and maybe you have a few friends who have some cards they can lend you? I have found it more economical this way.