Tiff,
You've got your answers already: a hope chest is something in which linen, clothing and other things are collected in anticipation of marriage. It's an old tradition, way back when, when a married couple would basically start off with nothing, and there wasn't the modern custom of having wedding parties and the *very* extensive use of gift registers.
The original idea was that the young woman herself would make or otherwise collect the things into the chest, over the course of many years. Now, it tends to be something that the bride's mother (or in practice both parents) give her, often in something like the very beautiful chests other posters have mentioned.
I think it's a beautiful tradition, but one that should be used selectively. It would probably be even better if the chest includes something that has been handed down in the family (such as heirloom linen) that the bride would then take out for special occasions, and in time pass on to her daughter.