Telnet is insecure garbage. If you have any choice in the matter, you want OpenSSH. Get it from Extras (or here). If not, there's a telnet client available here. Though, personally, I'd just ssh into another host and telnet where you need to from there.

nmap is available here.

If you mean ftp server then just use the sftp server in OpenSSH. If you need a client then something like MaemoFTP would probably suite your needs.

As always, Google* and Gronmayer are your friends.

*Google Pro Tip: Adding the word "maemo" to your searches on google will almost always get you the result you're looking for!