Cellphone Memory

A couple of years back, there was no relation defined between cellphones and user memory area. Soon with the onset of imaging and multimedia features into the cellphones, the memory requirement was must. A huge built-in memory could drastically increase the price; hence memory slots were introduced so that each user could satisfy itself upto its own level. Nowadays cellphones have normally 2Mb-16Mb built-in memory pool and an additional memory slot. Below I will discuss the available solutionMultimeida Cards, MMC and RS-MMC
Nokia and some other important cellphone companies use the standard of MMC slots for memory. MMC cards are very light, flash based and around the size of a postage stamp. MMC is also used by devices such as digital cameras and mp3 players. Their size normally varies from 32 MB to 512 MB.
RS MMC i.e. reduced size multimedia cards are almost half the size of MMC cards. They are more efficient to use and adapters are avialable to use RS-MMC cards as MMC or SD cards.
Memory Stick and Variants
Sonyericsson smartphones usually use the memory stick interface to fulfil their memory requirements. There are 3 versions i.e. Regular, Duo, Pro. Regular is somewhat longer in size than others and the first one to be introduced. Adapters are available to use Duo and Pro as regular. Duo provides maximum size upto 1GB while Pro can handle upto 2GB.
Secure Digital (SD) and SDIO
SD cards provide a more advanced concept. You might think that as your desktop computer has a universal interface i.e. USB so that you can connect a variety of devices with it. Then why not a standard interface for cellphones ! . SD comes to fulfil this key goal of standardization. Nowadays advanced cellphones have a standard SDIO interface. In the market, devices are available (eg Memory, Camera, GPS, Modem, Bluetooth, Wifi) with an SDIO interface. So, technically you can connect these devices with your cellphone/smartphone/PDA.
This technology still needs some work to be done but I am sure that it will lead us in the coming years.

Conclusion
All these types have almost similar price and speed; only the technology, shape and lack of standardization matters. Sometimes it matters that the memory is plug and play or not. Like in some cellphones, you have to switch the cellphone off before changing the memory card while in the newer ones, memory is plug n play.
To provide an interface of such cards with your PC, universal or specific USB card readers are available with very cheap price in the market.
This area is close to standardization and I am sure that we'll see something different in the coming quarters.
Memory Typess in current situation.