kebtek, I don't personally use those $100 services, but I have some developer friends that do and I've never heard any complaints. If you have a budget you can get listed in Yahoo's directory and some other industry specific directories within days. That is not going to help you with ranking though.
If you need to get listed quick and ranked well, you should consider adwords. Adwords can be very cost effective if done properly. First you can set your own daily budget. If you have $10 per day to spend, that's all you will spend. The trick is getting enough traffic or clicks for that $10 per day.
Try doing some keyword research for your client. I personally use keyworddiscovery and wordtracker, but they do cost money to use. You can do keyword research for free using google's keyword tool.
Search for single words first and look for potential keyword phrases your client's demographic could be searching for.
Target phrases that have a higher search volume vs competitors.
See how much it is going to cost you to get in the top 5. Drop out the keywords that are expensive assuming you are on a budget.
Target the inexpensive keywords that will give you the most traffic and good ad positioning.
This can work very nicely for you and will keep your budget it check.