Re: Please recommend inexpensive interface & mic
I don't know what the definition of inexpensive is, so I may be going outside your budget.
I'd watch ebay for a yamaha audiogram 3 for under $40 for your interface. Make sure it includes the software. There are probably better options for $30 more, but the audiogram is simple and will work for one mic.
For the mic I'd watch ebay. Rather than a 57, I'd look for an AT2020 as a good low priced condenser mic. There's also the AT2035 which I think includes a high pass filter and 10db pad. Or, my choice, an AKG Perception 220 mic. I got the P220 new for $101.50 and $5 S&H on ebay. like the AT2035, it has a high pass and pad. I also came in an ok case with a shock mount.
You'll want a stand too. I think any of those mics will give you more versatility than the SM57, but they won't be as bulletproof.
One more thing, the AT2020 can also be bought as a USB mic. It may be slightly better than the Samson Bo mentioned, but 6 of 1, 1/2 dozen the other...