Endless are you talking about websites that you can bid on jobs that people post? I don't know of any of them that are worth your time. I bet they are out there but if someone on here uses one I bet they don't want the extra completion.
For schools there is no bidding in my area. They just have a preferred vendor list. Just call the school. In my area they do one list for the whole city. I get alot of school business but keep in mind they pay with PO's. You have to pay for everything up front then they pay within 2 to 4 weeks. (most of the time)
For Cities I have never tried. I know they have alot of work but the competition gives them contract pricing or better and you have to pay for items up front also.
If your looking for work. try these ideas:
Print up a simple postcard with sale prices and hand it out, put it on cars, go door to door. (I used to put one on every company truck I saw parked.)
Email all your old clients. Just let them know you have a great new press and are looking forward to working with them again.
Call service companies (landscaping, painters, janitorial, pool cleaners, etc.. They need uniforms and they go threw them fast. Great source of repeat business.
Do contract work. (find Embroiders that don't offer screen printing and offer them your services at a discount so they can make some money.)
Hope this helps.