Best to download and store in plain text files, i.e., as source code. Use a .BAS extension.
If all you want to do is have a repository of routines, store these .BAS files in a single directory. You may also want to add comments beginning with 'keywords: and synopsis: at the top of each file in order to make searching easier. For the first, add a few keywords after the colon, e.g., for a Sieve of Eratosthenes function, maybe the keywords sieve Eratosthenes prime. For the second, add a brief description after the colon.
If you also want to track any changes you may make, you may want to consider a revision control system/versioning system. Myself, I only trust plain vanilla RCS, and I use commandline tools to maintain source code, including VBA. I'm odd that way. You may prefer GUI systems. I can't recommend any.
