How big are the memory sticks that are avalable yet? And is there any limit to the amount of memory they could cram into one?

You have 1-, 2- and 4 Gig cards

I don’t think the 4 gig is in production yet. However, there is a 4GB removable hard drive available for the PSP.

There are several different amount of memory for memory stick Duo’s. 32MB, 64MB, 128MB, 256MB, 512MB, 1GB, and 2GB (and 4 GB coming soon, but be prepared to spend big bucks for it)

Keep in mind there are regular Duos, Pro Duos, and High Speed Pro Duos. As long as there is the word 'DUO' on the memory stick, it will work with the PSP, but the Pro is faster than the regular Duo, and the High-speed is even faster (at loading the data).

I have a 256MB memory stick, and I won't need a bigger one for a while. I use my 20GB iPod for music, and all my photos (many of which are backrounds made by Fman) take up less than 50MB. For videos, I put whatever new PS3 videos we get onto the PSP, and any full-length movies I'll just purchase on UMD.

ok, i do have an ipod, but how many (medium quality, medium length) songs would you get on a 512mb mem stick?