It depends on what you are looking for. There is a seed exchange here at GW where you can trade for just about any seed. Some people do SASBE offer where they send you seed for postage. There are lots of companies that you can order seed from. What are you looking for?

Have you looked into the Farmers and Consumers Market Bulletin?
Lots of people in the State of Georgia sell their home grown seeds for very little (usually the cost of the packaging). It's a fun way to get neat seeds.

The bulletin itself is free.

http://agr.georgia.gov/00/article/0,2086,38902732_39654299_40311428,00.html

When I first found GW and WS- I tried to find folks who had seeds I was looking for and sent an e-mail out to them asking if they wanted to swap for what I had to offer. There were many folks who never responded- but of those that did some really were generous in giving many more wonderful seeds than were arranged for- my eternal thanks to those generous souls who showed me how to swap in GW.
I was then introduced to the Exchange Forum (round robin)and entered into a few exchanges there- What a GREAT find! I was able to send in seeds I had to share- and received many different seeds in return! It is and probably always will be a highlight in my yearly garden seed procuring. There are many great ones going on right now!
Sometimes I get just what I am hoping for- and many many times- I receive things I never knew how much I would love!
Every year I try new things that have been sent my way- and gather seed from everything (everywhere) and send them on to be grown on by others- It is hard in your first year trying to find enough seeds to swap- but Trudi and Bakemom are doing wonders for newbies with their seed projects! Sending SASEs, Self Addressed Stamped Envelopes back to folks filled with new things to try.
Keep your eyes peeled here as well, as folks do tend to share information as to where the great seed deals are on the web. I know almost every web seed purchase I have made is because of "sale" postings listed here in this forum.
Check my swap list and see if there is anything of interest to you- click on the blue underlined "my page" behind my name- You'll find it! Send me an e-mail from my page as well if you see something you like.
Your gonna love wintersowing!

Have you found the wintersowing exchange page? Many SASBE offers there on seeds which are good for wintersowing. Also Trudi's offer on her site.

Some less expensive online companies
valueseeds.com
cheapseeds.com
seedsandmore.com
wildseedfarms.com

Here is a link that might be useful: Trudi's site

A few other companies you can check on line that I like are:

Sand Hill Preservation
Pinetree Seeds

They have very reasonable prices. You can also request their catalogs.

I would try the exchange pages on the Gardenweb first. I've been able to get the vast majority of what I wanted to grow by trading or by the kindness of others.

Here is a link that might be useful: Exchanges and Trades

As someone mentioned - a lot depends on what you are looking for in "unique" and also what you consider a good price (lusting after some $14.99 plus shipping catalog plant? Suddenly the seed seems reasonable).

I find JLHudsonseeds.net carries a lot of seed that others don't. Just placed an order Thursday eve online and it arrived today. Great turnaround. My first year with them so can't talk yet to germination. The catalog is a list so you need to know what you're looking for (no pictures) or keep 2 windows open with one google image search. Good prices and shipping is just $1.50. I'd say start there.

Next I'd check out Summer Hill Seeds - also my first year with them, she has a good selection, prices better than most and was also very speedy.

Pinetree is a stable of mine - more robust selection of veggies, pretty normal fair on flowers.

Swallowtail Garden Seeds isn't cheap but also has a few things others don't carry.

I also use Parks and Select Seeds.

I'll agree with J L Hudson, I've had great experience there, & very reasonable prices for hard to find seeds.

If you will list what you are looking for, I bet we could help you :)

Lisa

Bumping this to top as we have questions about Seed suppliers: Burpee, who instead of Parks and Grass. Lots of good info in this thread.

I really like Pinetree Garden Seeds (www. superseeds.com) - they sell smaller packs for $.95-1.75, so I can try things without necessarily having to buy 100s or 1000s of seeds at once. They have more veggies than flowers. For more unusual things, I like Select Seeds (www.selectseeds.com) - they're not the cheapest, but they feature heirloom flower seeds and plants. I've gotten some beauties from them, and I'll be placing another order from them this year to try some new goodies. Seeds of Change has many unusual and heirloom varieties of veggies, herbs, and flowers, but again they're not the cheapest.

So far the best selection of seeds I ever received was through a seed exchange here on GW - people were amazingly generous in sharing their seeds, and I've got so many new things to try now. I simply shared some of what I already had, and received new things in return, for the cost of a little time and postage. It was a bargain.

Laurel

Hi, Rjinga:
I started an account at eBay many years ago and love them because they have such unique seeds listed there, and there are many reputable vendors.
This year I used Flower Angel, Pase, and Meadow Mountain, among a few others.
Also the prices are often quite low--often at .99. Usually no more than $2.25.
You can bid on seeds, or you can buy seeds--they have both types of sales.
I do a bit of both, but because there are so many options, there are always plenty of choices.
What I do is search for what I want, then check the vendors store to see what else they have. That's how I get the combined shipping deals. I tend to stick with the same vendor for as many seeds as I can get.
They have a feedback rating for each vendor so you can see how reliable they are.
The vendors always combine shipping, so usually I just pay $1.50 shipping and get quite a few seed packs for that.
This is the biggest area of savings.
There are small and large vendors and eBay--but all of them generally use padded envelopes, plastic seed packs, and computer printouts with photos, instructions and invoices.
I will post pictures this year of how the gardens comes out, using mostly eBay seeds.