If you have a valid US visa (I have a B1) and are returning from the US, you can stop over in Singapore without visa for upto 4 days (96 hours). But your entry is at the discretion of the immigration officer processing your stop over request.
I am planning a family trip in Singapore on my way back and I could not take that chance. Possession of a tourist visa gives me a sure shot chance and so I looked up applying for a Singapore visa through the embassy at San Francisco.
The process is a cakewalk. The required documents are
1. Visa application form filled in (For address put in your India address as well as your US local address with phone number and email address)
2. Your original passport with a copy of the first, last and the US visa pages.
3. Copy of invitation letter for your business trip in US. ( I am on B1 so this is mandatory, for L1, H1B could be waived)
4. Copy of flight e-ticket. (Obviously your itinerary should have a stop over in Singapore)
5. Copy of your hotel confirmation voucher in Singapore. (do the booking before hand, better to get some good deals)
6. 1 passport sized photo, maintain a white background, I think the size does not matter.
7. Self addressed US postal express return envelope - flat rate $17.50. (Write your US address in the recipient columns, ensure that the postage is pasted on the cover)
8. $20 in cash.
Drive in, or take the BART (to Montgomery station) to 595, Market street, SF. The embassy is on the 24th floor, suite 2450. Give the documents to the receptionist and get them verified. Pay the cash and collect the receipt and you are done. Note the submission hours are from 9 am to 12 pm only.
Drive or take the BART back home. I drove the rental car out to Milbrae, parked at the BART station and took the BART to get to SF and back. I did this (submitted the application) on a Monday morning and I received the stamped passport on Wednesday.
If you want to pick up your passport from the embassy office directly, skip the US postal express return envelope, will save you some money, but adds on to some extra effort. The collection hours are from 2 pm to 4 pm. The receptionist will actually let you know when to come for getting your stamped passport.
You can also send your application and supporting documents to the embassy via post, but then you need to make sure that you have a draft for the processing fee of $20. I skipped this part just because I did not want to go over the hassles of going to the bank. I don't know if we can do that if we do not have a SSN.
If you want some other detail on the process look it up on Embassy@SF site, or send put in a comment/send me a email.