Skipjack was written and is used by the USA's National Security Agency (NSA), so it is obvious that they consider it secure. It is an 80-bit code using 32 rounds of coding, but the algorithm is classified by the NSA. The other thing notable about Skipjack is that the NSA have built a 'trapdoor' into it, whereby any coded massage can be translated by someone with a 'master key' (i.e. the NSA.). So although it seems secure, it is not secure to the NSA, merely to everyone else.
RC4 was designed by RSA Data Security, and is very fast. However this may cause it to be less secure, and Netscape's SSL (which uses RS4-40) has been broken by more than one independent group in recent times. The algorithm ceased being a secret at RSA when someone posted the source code on Usenet news.
Blowfish is another new cypher, and was developed by Bruce Schneier, a leading modern cryptographer; other symmetric cyphers are those mentioned before, such as Enigma and the Vinenère Cypher.
However, there is still the problem of that key-distribution...