To Help Sometimes Money Is The Simplest & Best Answer
Many will go to help, hands-on assistance of course will be needed. But some can't go, and want to help, so they will look to make a donation. Often we think of donating items, its personal to us to give something tangible. But in the end, the simplest way is usually the best. in this case that means donating money. It may seem impersonal, you may think you understand what is needed and want to donate something, but with money, those on the front lines can purchase what is truly needed. More after the break on that, but if you just want to cut to the chase - you can donate to Red Cross here.
CBS did a far better piece on this than I can write, I recommend you read it here. The gist is that stuff is just that, stuff. You may think your old jacket is good for someone (its summer), or your bear would be great for a child (they need food first), and in the end someone has to move, and sort, and store that stuff. It can be a huge mess. But money, they can use the money on what they know people need now.
Sure, eventually people will need clothes, children will need toys and books, and later you can get in on helping rebuild that. But right now they just need to survive, and that means shelter, and food, and water. And that is best gotten by money by the organizations that can buy and mobilize it. They can buy in bulk so they can get more out of the money, they have the methods to get it there and distribute.
In addition to the American Red Cross, there are other national organizations and if you do some research you can find them, just make sure you are donating to a reputable organization, and again money is usually best even if they list other supplies. Local food banks are great organizations to consider besides national ones. I could go on, there are many worthy organizations (don't forget about all the pets affected), but there are lists of lists all over and again you can do your own research.
Think outside the box too. You may not be able to donate as much as you want, but you've got some stuff you don't need. Instead of donating the items, hold a rummage to sell them and donate the money. Look for local events that will likely pop up to raise funds (again favor fund versus item donation events.) Another need is blood donations since blood centers in Houston can't do any right now they need it to come from other places. As a bonus, as I posted recently, the BloodCenter of Wisconsin right now has a deal to get Brewers tickets - with more stuff if you do at their Wauwatosa location.
Just please, please, if you want to help strongly consider money over things.
In a local connection, Wisconsin native J.J. Watt and Texas pro-athlete has donated $100,000 to relief efforts in matching funds to a crowdsourcing effort that has reached $500k as of this writing. Great Play Mr. Watt.