Although MSN is lagging behind both Yahoo and Google when it comes to the ways you can get your site indexed, it is still one of the top three search engines, and it should not be ignored.
MSN offers you two different ways to get your site indexed, and you should submit to both. However, before you do that, make sure that you have optimized your website first.
You can get more information on optimizing your site for MSN, as well as tips on search engine optimization, here:
The tips that you will find here basically apply to optimizing your site for any search engine, but they are definitely worth the read so that you focus your search engine optimization efforts in a way that will get your site indexed.
As I mentioned before, there are two ways to get indexed by MSN. The first involves submitting to the Inktomi index. The Inktomi index actually powers the MSN search.
Inktomi is now also part of Yahoo. However, you should still submit your site here. This will allow you to get indexed by hundreds of sites if your site is accepted.
You will need to use a valid email address for your site. Make sure that you use an email account that you actually use so that if there is a problem, you can promptly fix it. You may also need to confirm your submission.
Keep in mind that there are no guarantees on turnaround, and there are also no guarantees that your site will be accepted.
The second part of submitting to MSN is actually submitting to the MSN spider. Rob Benwell, of "Blogging to the Bank" fame, said that he used MSN for his searches when looking for niches, because MSN updates more quickly than either Yahoo or Google, and this was why he used MSN to test his results.