For me one of the best advantages of a digital SLR camera over a traditonal film type is the number of shots we can capture. In the old days (!) we would get at best 36 shots on a 35mm or incredibly only 10-12 shots on a medium format camera. Digital SLR cameras and memory cards have revolutionised photography!
I can remember photographing weddings and of course having to stop and re-load film - often at dififcult moments! If we choose the right memory card for our digital SLR camera we can take literally hundreds of shots.
Personally I never use anything smaller than a 1GB memory card. Of course formats of cards vary between cameras and you need to ensure you buy the right memory card for your particular digital SLR. Formats can be confusing to newcomers - SD, micro SD, SSD, compact flash and SDHC! Not only does using a large capacity memory card mean we can shoot hundreds of shots, we can shoot in the highest resolution our camera offers to ensure the best quality. If you want to blow up your best shots this is essential.
You can buy memory cards for your digital SLR so cheaply there's no need to scrimp on quality in your pictures. Compare prices of memory cards online to get the best deal. It's a mortal sin to me to go out on a photographic session wihtout packing enough high capacity memory cards in your bag!
In addition to brand names like Kodak and Fuji you will find cheaper memory cards from the likes of Sandisk and Lexar. It's worth checking any reviews but don't be put off by these cheaper alternatives for your digital SLR camera.