How should we dress when attending church? What are some verses from the Bible which instructs us on our attire when attending church worship services and activies?

Is "formal" dress good / bad / required / optional / recommended?
We are not commanded to dress a certain way in Scripture, other than that it should be modest.

However, I have a strong personal conviction - one I would not try to force on anyone else - that you should dress up for Church.  

When God appeared to Moses as a burning bush, He commanded Moses to "put off thy shoes from off thy feet, for the place whereon thou standest is holy ground."  To me, this implies that God expects us to respect Him, and approach Him with reverence, as one who is Holy and worthy of our best.  Therefore, I dress up, not to look good to others, but because it's such a small thing for the God who created me and saved me.

That said, I do not look down on anyone who doesn't feel the same.  Not everyone thinks the same way, and it's not for me to try to force them.  Christianity isn't about a bunch of rules and regulations, it's about our hearts, and our relationship with God.