The ones on .co would probably be the best to get at this point. It is a fair replacement for .com though not quite the same.
if by character you mean letter, than .org would be my investment choice. I would not bother with any digits for anything that is not .com/.net
thanks for ur reply guys...1 more question i need to ask is: I have around 20 3letters.net domains but all r new and recently registered, r those worth and which is the best place to sell them?
all of them are like: with numbers in it 0a1.net a0b.net are these worthy and which is the best place to sell them?
due to economy and stock market down turn, not much right now. you can sell them on ebay for about a registration fee if you don;t want to spend on renewals