So your budget resets in three weeks. What you're looking for then, is things that can be paid in advance. That should be doable; most companies, including educators, are happy to take money early.
So what are good kinds of professional development to spend it on? I would look at:
- Technical training
- Soft skills
- University degrees
- Technical conferences (idea courtesy of Stephan Branczyk)
There might be something you've always wanted to learn, and instead of taking a canned online course, you could spend the money on a course with more direct interaction with the teacher. Or take a particular course that always seemed interesting but wildly expensive.
Technical training ties in to certification; if you identify a particular certification as desirable, then take the training for the certificate.
Certification on the company's dime is awesome. Certification tends to be quite pricey. But it's a benefit to you and to your company.
For you, because it gives you more standing and prospects inside your company, but also value if after a few years you want to leave. (So pay attention to how fast you would need to re-certify.)
For your company, getting you certified helps them sell things to customers. "We can make product X for you because we have Y certified people."
To get an idea of what kind of certification might be relevant, go browse LinkedIn for jobs with your title or a step up on the ladder and look for specific certificates they call for. Also, look for key skills that get called for a lot and then google what the main certifications for that are.
Aside from certification in main platforms with which you build, look for certifications about "process": Scrum or ITIL, certification perhaps, or something related to security, or to testing methodology.
Hard technical skills are only part of professional development. To thrive in a company, you also need soft skills. Leadership, presentation, networking - all of these help your own career, but they also help your company because they make you do better work for the company. So it's legit to spend budget on it.
And don't think "well I'm a generally pleasant person so I already have soft skills". Because the scale goes up, up, up. No matter how good you are, there are people who are significantly better. Giving a presentation in a class in university is not the same as defending a multi-million budget in front of higher management. Those people are jaded, have seen thousands of presentations, and to blow them away you need to up your game.
If you inquire, I suspect a lot of part-time programs will allow you to pay in advance.
In the long run, higher degrees will help you if you want to get into the more innovative branches of your company.
I think these get more interesting if you pursue the MSc++ angle. For an innovative company, it can be good to keep ties with the academic world. If you have contacts with professors it gives you a possible lead on the really good interns, openings to uni/industry collaboration and an idea about upcoming new technologies. Also, recruiting people who are done with their CS Masters/PhD and looking to go into industry. Conferences are a lot about networking, building and maintaining relations.