I ve noticed that google index sites faster by coming through forum links than google url submission.Seems you can Get your site indexed by all the major search engines by posting a link to it on a forum. Use a webmaster forum and post in the section where there are website reviews. You can get your site reviewed by your peers and also get it indexed by all the Search Engines like Google, MSN, Yahoo, etc.
It is actually quite hard to get your forum indexed in the first place so I'm in a little doubt. it is possible however to install MOD's on forums to help the indexing. How did you find out that forum indexing is quicker ?
google index a site by submit a url to google or some other site link to it.
If the site witch link to your site to be indexed is not indexed by google or not active enough(lower page rank or idle for a long time), It will take a very long time for google to find your site link and index it.