Most of them are worthless. Also - any SE that wants your email address to index your site is a marketing scam. Any SE that wants $$$ is too (i'm sure most of you knew that, but let it not be claimed it wasn't said)
Get a link from any of the busier website (like dp forum) and your site is bound to be attracted by the search engine. Never pay to get crawled.
It depends on each site you wanted to be listed. Should you require a fast listing then you should pay a small fee for the submission providers to list your website ASAP.
Thats a petty smart answer. I was also thinking like that. Forum is the best place where we can gather knowledge and get traffic, backlinks as well.
Crawling is a free process and if some SE wants you to pay for something that is supposed to be done for free is something that you should stay away from.