I can't get remarried due to an unscriptural divorce. How am I able to help the congregation that I worship with, being that I am a divorced male? Also, if I give to the Lord as I have been prospered, can I take the extra money that I acquire and give to missionaries, needy saints, etc. of my choosing or do I need to put it all in the collection plate?
You can and should do the same things any other single male Christian in your congregation does. The only roles your situation blocks you from doing are those of deacon and elder. The rest is wide open. We have several divorced people in this congregation and they are assets to the group.
In regards to your giving, Peter told Ananias concerning his money, "While it remained, was it not your own? And after it was sold, was it not in your own control?" (Acts 5:4). A person can do as they wish with the funds God has blessed them with.
The one mistake, however, that I see some people make is assuming that if they give money to other religious activities, that it somehow relieves them of their obligation to support the work of their local congregation. The command, "On the first day of the week let each one of you lay something aside, storing up as he may prosper" (I Corinthians 16:2) still applies. In giving, Paul also stated, "For I do not mean that others should be eased and you burdened; but by an equality, that now at this time your abundance may supply their lack, that their abundance also may supply your lack--that there may be equality. As it is written, 'He who gathered much had nothing left over, and he who gathered little had no lack'" (II Corinthians 8:13-15).
So purpose in your heart what you will give to the work of the Lord in your area, and when you find yourself with excess further the work of the Lord by helping the work in other areas as well.