I love standards; there are always so many to choose from. The sequence read archive strives hard to capture appropriate information about the sequences that people deposit, but in the end scientists are people too, and they are never uniform and standard. This means there are a lot of ways to describe metagenomes. To get your data used by other people (and cite your papers), make sure you tag it so we can find it!
There is a lot of metagenomics data in the SRA, but it is not very well organized. To get it all, you need some wicked SQL-FU … or you can copy these recipes!