Still editing this list of things we've tried at Twilio, here's what I've got so far:
* Use the free version of everything, and when you run into the limitations tell the company you are working with that you are a startup -- they will likely make an exception for you, small businesses hold a place is many people's hearts
* Barter your time (instead of money) for things you really need, such as trading blog posts with a company you want to get free services from
* Become a customer of your customers - make non-monetary trades while you're both growing, because you have being cash-strapped in common (only do this within reason)
* DO NOT pay for a PR agency or do trade shows, find ways to hack these traditional promotional tactics (contact me if you want ideas, or check out constraintmarketing.com)
* Use GetSatisfaction for your online forums, the free version is pretty awesome. +1 Zendesk comment someone mentioned already
* Use Expensify for expense reporting (you'll need this as soon as you have your first sales/marketing type)
* If you have investors (even angels), try to get your investors to let you work out of their office space. Chances are they are on the road a ton and won't care
* When you're too big to borrow space, try a coffee shop that is dead during the day and make friends with the owner. They'll appreciate the regular business
* Coworking sounds expensive at "$500 a desk" but do it Hong Kong style, 2 or 3 people to a desk or coming in at different times during the day
* When you rent a space, try to get the previous tenants to throw in the furniture they're going to have to pay to dispose of anyway
* Don't do company credit-cards until you absolutely have to, the founding team should be willing to take the personal risk and be responsible for late fees (heaven forbid)
* Order promotional materials from Fedex or Office depot - a business account gets you 20% of everything. A single good-looking retractable standup banner looks professional, travels well, and lasted me over a year at our startup before we had more swag
* Pick ONE promotional giveaway item, make it awesome, and order in bulk. This will save you money long term, while still building brand, but don't both having pens, keychains, dongles, widgets, gadgets, etc. try just a tshirt
* set a travel policy about the cost of flights, and take public transportation instead of cabs. Remember, you are cash poor and time rich (sort of). Look for deals like the JetBlue all-you-can-eat or Virgin America $39 flights, snag them, and figure out who to visit at those destinations
* buy a coffee maker and those little K-cups from Bed, Bath, and Beyond -- you'll save a TON on going for Starbucks, both in time and money. In SF a latte costs $4!
* Strike up a regular "rate" with a single restaurant where you take all your clients, potential investors, etc. so that you can still treat them well but save 20-30%
and of course I have to say:
* use OpenVBX to set up a business phone line with a simple menu that forwards to various cell phones "press 1 for support, 2 for sales, etc." and only pay for what you use