I've bought a 512 MB miniSD card manufactured by ATP and I've placed inside my Orange SPV C500, so now I have much more storage space. Finding a 512 MB miniSD card in stock was quite challenging since many stores listed the item (but temporarly sold out) but I found only in one e-store the item in stock at a resonable price. By the way it was 65 USD with free shipping, and I think it is a good price since the transfer rate they list is quite good (10MB/sec, if I remember correctly).
Also I've noticed that using this card also gave me more available memory, as now when I restart the phone I have 41% available memory, and with the 16MB card that came with the phone it was around 30%. Did anyone have an explanation or is it magic? So I moved my pictures and now I have space for music also. A Bluetooth headset is on my buying list so I could listen mp3s. A case is also on my list but a 25$ Krusell is quite out of my league.