The point of a salt is that it is unique, so that an attacker who wants to crack multiple hashes has to do all the work afresh for each hash. If you include a characteristic that is derived from the password, it doesn't help the salt. It doesn't hurt, either, but it doesn't strengthen the salt in any way.
In effect, by taking
hash(password+length+salt) instead of
hash(password+salt), you're using a different hash function
hash2(x) = hash(x+length(x)). You are effectively inventing your own cryptographic primitive. That in itself is a bad sign. I don't think the result is actually insecure in any way, but I'd still veto it as an unnecessary risk.
hash2 is very marginally slower than
hash. Slower is good for a password hash, but there are better ways of making the hash slow — password hashing functions have a tunable parameter to configure the slowness of the hash. Using a variant hash isn't worth the added complexity.
The normal method to generate the salt is to make it random. If you're going to add anything to it, the only point would be to mitigate a bug in the random number generator. If you're going to do that, take something that does not depend on the password, such as the user ID or the time.
Be careful with taking the hash of a concatenation of two strings: it's ambiguous:
hash("bob" + "swordfish") = hash("bobsword" + "fish"). Whenever you take the concatenation of some strings and hash them or otherwise use them in a cryptographic protocol, make sure that the strings can be decomposed unambiguously. If there's a byte value that can't occur in either string (null bytes are often suitable), use that as a separator. If there is a bound on the length of the first string (264 is often suitable), prepend the length (itself in a fixed-size encoding, e.g. 8 bytes for a 264 length limit). If you're building complex data structures, use your library's ASN.1 module.
In any case, when you need to store a password hash, you shouldn't think about cryptography. Use your programming environment's bcrypt or PBKDF2 or scrypt library.
For everything you wanted to know about hashing passwords, everything you didn't want to know about hashing passwords, and everything you didn't even know you might know about hashing passwords, read How to securely hash passwords?